I'm going to inadvertently make my roommate sleep elsewhere
Are you going to do that because you're fearful of something or it's been already planned?
Fear, I think he's having inappropriate interactions with my girlfriend
I'm sorry you have such suspicions, but your roommate owns part of the house too and you have no right to tell him what to do. You should be the one sleeping elsewhere if you're not comfortable with him, or move out.
Hmm. Okay, I'm going to sleep out.
I think that is for the best in this situation.