Most Helpful Guy
Ok, so after reading your post this is what i believe to be the most likely situation. As youve already stated, he may be an introvert. You also stated that you're likely out of his league, at least physically. I believe that he may be in a slight state of shock/disbelief as a result of the non-conventional pairing. Also, keep in mind that despite the friendly nature of his roommates, they could possibly, for whatever reason, be running interference.
Id suggest you try ro engage him on the level that you attracted you to him initially; intelectually. Meet him on the level with which he is comfortable. Call him, talk to him, take your physicality out of the equation and give him and his ego the opportuniry to gain some confidence with you and in the relationship. If that dorsnt help matters, sounds like you may need to move on?