I agree with most of the other commenters. I’m not seeing mental instability and danger here.
FWIW, there are so many students who don’t get along with their roommates. My D and her first year roommate didn’t care for each other. D spent a lot of time not in her room, and I think the roommate did the same. . It wasn’t great, but it wasn’t horrible and she got through it. I fully agree that your son needs to advocate for himself and just get through this. My D is a conflict avoider but her way of resolving it was to remove herself from the awkwardness s much as possible. Not what I would have done, but it worked for her.