My former roommate (female) and I were the best of friends before her boyfriend eventually started staying with us so often that I felt uncomfortable being in my own apartment, despite being really close friends with both of them. They would argue in front of me, and also not be quiet about having sex with me still in the apartment. It soured our friendship to the point that I had to ask her boyfriend to go back to his own place after he stayed nearly every night for two months. Living with your significant other changes the dynamic of your housing situation, whether you've got roommates or you're living on your own. So even if you argue that the two of you don't act all lovey-dovey around the roommate, nobody wants the be the awkward third wheel, especially in their own home. You'd be putting him in an extremely uncomfortable position and that's really not fair to him. If you and the bf want to move in together I'd suggest finding a place on your own.