Sounds like your dog knows your room mate is scared of him. I would suggest letting her take over the feeding, walking etc. These two activities are the things dogs love most therefore if she takes control of this he will soon realise she is a friend and part of the house hold. I know she may not be keen to do this but she really needs to put in some work as I think that if she remains scared of him he will feel more and more dominant over her and the situation may escalate. Good luck!