Riverside Resources Expands British Columbia Rare Earth Elements Property Portfolio with Taft Project Acquisition

Radisson Mining Resources Inc. (TSXV: RDS,OTC:RMRDF) (OTCQB: RMRDF) ("Radisson" or the "Company") is pleased to announce that it has filed a technical report prepared in accordance with National Instrument 43-101 — Standards of Disclosure for Mineral Projects for the O'Brien Gold Project ("O'Brien" or the "Project") located in the Abitibi region of Québec. The report is titled "O'Brien Gold Project Technical Report and Preliminary Economic Assessment, Québec, Canada." A copy of the technical report is available under the Company's profile on SEDAR+.

The O'Brien Preliminary Economic Assessment ("PEA") describes a high value project based on the use of neighbouring milling facilities for the processing of mined material, reducing capital costs, development risk, and project footprint (see Radisson news release dated July 9, 2025). It represents a "snap-shot" study for the Project, utilizing the existing Mineral Resource Estimate ("MRE"), re-blocked with an updated cut-off yielding more ounces in more tonnes with good continuity at a lower average grade. An ongoing 50-60,000 metre drill program at the Project is currently delineating new gold mineralization outside the scope of the MRE and the initial mine design, including below the historic O'Brien mine workings.

Highlights of the PEA include:

• After-tax Net Present Value at a 5% discount rate ("NPV_5%") of $532 million, Internal Rate of Return of 48%, and payback of 2.0 years at US$2,550/oz gold ("Au").
• Initial Capital Cost of $175 million and Life-of-Mine Sustaining Capital of $173 million.
• Cash Cost¹ of US$861/oz and All-In Sustaining Cost¹ of US$1,059/oz including conceptual 30% toll milling margin on processing and G&A costs.
• Extremely capital efficient with after-tax NPV_5% to Initial Capital Cost ratio of 3.0 at US$2,550/oz Au.
• 11-Year Mine Life with 740 koz mined and 647 koz recovered at 87% average recovery with a gravity-flotation-regrind-leach flowsheet.
• 70 koz/annum average steady-state gold production (Years 2-8) at an average annual after-tax Free Cash Flow¹ of $97 million.

The PEA was completed by Ausenco Engineering Canada ULC as lead consultant with specific responsibility for metallurgy, processing design, infrastructure and financial modelling. InnovExplo (a member of Norda Stelo Inc.) completed the mine design and mine scheduling, BBA Inc. were responsible for water management, surface facilities, and a review of the Project's environmental assessment procedure and permitting requirements, and SLR Consulting (Canada) Ltd. were responsible for the MRE.

Qualified Persons

Disclosure of a scientific or technical nature in this news release was prepared under the supervision of Mr. Richard Nieminen, P.Geo, (QC), a geological consultant for Radisson and a Qualified Person for purposes of NI 43-101. Mr. Nieminen is independent of Radisson and the O'Brien Gold Project.

The PEA is authored by Renée Barrette of Ausenco Engineering Canada ULC, the Qualified Person responsible for the preparation of the sections in the PEA on the Project's milling assessment, metallurgy, and the financial model which is based on capital costs, operating costs, and the mining cost provided by other parties; Mr. Luke Evans, M.Sc., P.Eng., ing, of SLR Consulting (Canada) Ltd., the Qualified Person responsible for the preparation of the MRE at O'Brien; Mr. Marc R. Beauvais, P.Eng. of InnovExplo, a member of Norda Stelo Inc., the Qualified Person responsible for the sections in the PEA on the mine design and mine scheduling, and; Mr. Hugo Latulippe of BBA Inc., the Qualified Person responsible for the sections on permitting, environmental, social, water management and closure cost estimate in the PEA. Each of Ms. Barrette, Mr. Evans, Mr. Beauvais and Mr. Latulippe have reviewed and approved the technical information contained in the PEA in their area of expertise and are considered to be "independent" of Radisson and the O'Brien Gold Project for purposes of NI 43-101.

Non-IFRS Financial Measures

The Company has included various references in this document that constitute "specified financial measures" within the meaning of National Instrument 52-112 Non-GAAP and Other Financial Measures Disclosure of the Canadian Securities Administrators, such as, for example, Free Cash Flow, EBITDA, Total Cash Cost and All-In Sustaining Cost. None of these specified measures is a standardized financial measure under International Financial Reporting Standards ("IFRS") and these measures might not be comparable to similar financial measures disclosed by other issuers. Each of these measures are intended to provide additional information to the reader and should not be considered in isolation or as a substitute for measures prepared in accordance with IFRS. Certain non-IFRS financial measures used in this news release and common to the gold mining industry are defined below.

Total Cash Cost and Total Cash Cost per Ounce

Total Cash Cost is reflective of the cost of production. Total Cash Cost reported in the PEA include mining costs, processing & water treatment costs, general and administrative costs of the mine, off-site costs, refining costs, transportation costs and royalties. Total Cash Cost per Ounce is calculated as Total Cash Cost divided by payable gold ounces.

All-in Sustaining Cost (AISC) and AISC per Ounce

AISC is reflective of all of the expenditures that are required to produce an ounce of gold from operations. AISC reported in the PEA includes total cash costs, sustaining capital, expansion capital and closure costs, but excludes corporate general and administrative costs and salvage. AISC per Ounce is calculated as AISC divided by payable gold ounces.

Free Cash Flow (FCF)

FCF deducts capital expenditures from net cash provided by operating activities. Management believes this to be a useful indicator of our ability to operate without reliance on additional borrowing or usage of existing cash. Free cash flow is intended to provide additional information only and does not have any standardized definition under IFRS and should not be considered in isolation or as a substitute for measures of performance prepared in accordance with IFRS. The measure is not necessarily indicative of operating profit or cash flow from operations as determined under IFRS. Other companies may calculate this measure differently.

About Ausenco

Ausenco is a global company redefining what's possible. The team is based out of 21 offices working across five continents to deliver services worldwide. Combining deep technical expertise with a 30-year track record, Ausenco delivers innovative, value-add consulting, studies, project delivery, asset operations and maintenance solutions to the minerals and metals and industrial sectors (www.ausenco.com).

About Radisson Mining

Radisson is a gold exploration company focused on its 100% owned O'Brien Gold Project, located in the Bousquet-Cadillac mining camp along the world-renowned Larder-Lake-Cadillac Break in Abitibi, Québec. A July 2025 Preliminary Economic Assessment described a low cost and high value project with an 11-year mine life and significant upside potential based on the use of existing regional infrastructure. Indicated Mineral Resources are estimated at 0.58 million ounces (2.20 million tonnes at 8.2 g/t Au), with additional Inferred Mineral Resources estimated at 0.93 million ounces (6.67 million tonnes at 4.4 g/t Au). Please see the NI 43-101 "O'Brien Gold Project Technical Report and Preliminary Economic Assessment, Québec, Canada" dated August 20, 2025, and other filings made with Canadian securities regulatory authorities available at www.sedarplus.ca for further details and assumptions relating to the O'Brien Gold Project.

Forward-Looking Statements

This news release contains "forward-looking information" within the meaning of the applicable Canadian securities legislation that is based on expectations, estimates, projections, and interpretations as at the date of this news release. Forward-looking statements including, but are not limited to, statements with respect to the ability to execute the Company's plans relating to the O'Brien Gold Project as set out in the PEA; the Company's ability to complete its planned exploration and development programs; the absence of adverse conditions at the O'Brien Gold Project; the absence of unforeseen operational delays; the absence of material delays in obtaining necessary permits; the price of gold remaining at levels that render the O'Brien Gold Project profitable; the Company's ability to continue raising necessary capital to finance its operations; the ability to realize on the mineral resource and mineral reserve estimates; assumptions regarding present and future business strategies, local and global geopolitical and economic conditions and the environment in which the Company operates and will operate in the future;, planned and ongoing drilling, the significance of drill results, the ability to continue drilling, the impact of drilling on the definition of any resource, and the ability to incorporate new drilling in an updated technical report and resource modelling; the Company's ability to grow the O'Brien Gold Project; the ability to negotiate and execute an arrangement with IAMGOLD related to the Doyon Mill on satisfactory terms or at all; and the ability to convert inferred mineral resources to indicated mineral resources.

Any statement that involves discussions with respect to predictions, expectations, interpretations, beliefs, plans, projections, objectives, assumptions, future events or performance (often but not always using phrases such as "expects", or "does not expect", "is expected", "interpreted", "management's view", "anticipates" or "does not anticipate", "plans", "budget", "scheduled", "forecasts", "estimates", "believes" or "intends" or variations of such words and phrases or stating that certain actions, events or results "may" or "could", "would", "might" or "will" be taken to occur or be achieved) are not statements of historical fact and may be forward-looking information and are intended to identify forward-looking information. Except for statements of historical fact relating to the Company, certain information contained herein constitutes forward-looking statements. Forward-looking information is based on estimates of management of the Company, at the time it was made, involves known and unknown risks, uncertainties and other factors which may cause the actual results, performance or achievements of the companies to be materially different from any future results, performance or achievements expressed or implied by such forward-looking information. Such factors include, among others; the risk that the O'Brien Gold Project will never reach the production stage (including due to a lack of financing); the Company's capital requirements and access to funding; changes in legislation, regulations and accounting standards to which the Company is subject, including environmental, health and safety standards, and the impact of such legislation, regulations and standards on the Company's activities; price volatility and availability of commodities; instability in the global financial system; the effects of high inflation, such as higher commodity prices; the risk of any future litigation against the Company; changes in project parameters and/or economic assessments as plans continue to be refined; the risk that actual costs may exceed estimated costs; geological, mining and exploration technical problems; failure of plant, equipment or processes to operate as anticipated; accidents, labour disputes and other risks of the mining industry; delays in obtaining governmental approvals or financing; risks relating to the drill results at O'Brien; the significance of drill results; and the ability of drill results to accurately predict mineralization. Although the forward-looking information contained in this news release is based upon what management believes, or believed at the time, to be reasonable assumptions, the parties cannot assure shareholders and prospective purchasers of securities that actual results will be consistent with such forward-looking information, as there may be other factors that cause results not to be as anticipated, estimated or intended, and neither the Company nor any other person assumes responsibility for the accuracy and completeness of any such forward-looking information. The Company believes that this forward-looking information is based on reasonable assumptions, but no assurance can be given that these expectations will prove to be correct and such forward-looking statements included in this press release should not be unduly relied upon. The Company does not undertake, and assumes no obligation, to update or revise any such forward-looking statements or forward-looking information contained herein to reflect new events or circumstances, except as may be required by law. These statements speak only as of the date of this news release.

Please refer to the "Risks and Uncertainties Related to Exploration" and the "Risks Related to Financing and Development" sections of the Company's Management's Discussion and Analysis dated April 29, 2025 for the years ended December 31, 2024, and the Company's Management's Discussion and Analysis dated May 28, 2025 for the three-months ended March 31, 2025, all of which are available electronically on SEDAR+ at www.sedarplus.ca. All forward-looking statements contained in this press release are expressly qualified by this cautionary statement.

Neither the TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this news release. No stock exchange, securities commission or other regulatory authority has approved or disapproved the information contained herein.