Partners Group Holding AG (SWX:PGHN) is in advanced talks for a potential acquisition of Rosen Group, a European engineering firm specializing in testing oil and gas assets, people with knowledge of the matter said. The Swiss private equity firm is emerging as the likeliest buyer for Rosen after beating out other bidders, the people said. It?s now trying to negotiate final terms of a deal, according to the people, who asked not to be identified because the information is private.