Location: Temeria Partisan Hideout
Locate Roche’s hideout in a rocky gully surrounded by woods, north of Oxenfurt. He is always willing to help you, but he (and Ves) can only make the journey to Kaer Morhen once you finish the following:
Complete Secondary Quest: An Eye for an Eye. Once finished, Roche agrees to help you, and both him and Ves will appear in Kaer Morhen (and question your judgment if Letho is also there).