He has to basically go out with his new roommate he was drunk upset over getting rejected ended up having sex because of it feels happy that someone wants him and because he has nowhere else to go he is willing to go out with his roommate. If he said he didn't want to go out with him it would make things awkward and his roommate might decide to kick him out because he was rejected to. He's trying so hard to survive. If it was me I would probably do the same just to have a place to stay at and come home to.
I'm still so obsessed with this manga I keep checking the comments section here either waiting for the translator to say something or for a new chapter come out. I'm losing it people hope you will still translate translator!
I feel ya honey ┗( T﹏T )┛