The RPA team will be combined with SLR's existing mining and minerals practice globally.
"RPA is recognised as a worldwide leader in mineral resource and mineral reserve estimation in compliance with all reporting codes; technical due diligence for mergers and acquisitions, financings and exchange listings; mineral property valuations, independent engineers for project debt financings, and expert witness in international litigation and arbitration cases," SLR explained.
"[Our companies] have collaborated on client projects for several years, and together we will now be able to offer our clients in the mining sector a complete service extending from value creation and generation through resource and reserve work to environmental and social risk and liability management."
SLR's takeover of RPA is the company's fourth acquisition in just over six months.
Officials said it is proof of the confidence both it and new investors Charterhouse Capital Partners have in the market and the company's capabilities.
"We have always been strong on service delivery for our mining and minerals clients, but the addition of the RPA team really lifts our advisory capability to another level," chief executive Neil Penhall said.
RPA has locations in Toronto, Canada; Denver, Colorado, US; Quebec City, Canada; and London, UK.
No timeline for the closure of the deal was released.