AB said it best.
He has waay overstepped his bounds and then next time he presumes to do ANYTHING with your dog, he is gone. I would also tell your roommate that this is a deal breaker. If he touches your dog again and it is the last time he is allowed in the house. And if he is half the db he sounds like, I would make sure he is NEVER left unattended with your dog and he is never allowed in the house when you are not there. If your roommate can't respect that, then she too needs to leave.
Sorry if that sounds harsh, but you made a lifetime commitment to your dog - not her and definately not to him.