Until We Meet Again by Christina Lee

Bruce “Bones” Lanning and Emil Ettinger had a decent roommate arrangement at Roosevelt College—other than Bones leaving his dirty socks lying around—so they agree to share the same space again. Their relationship has always been ridiculous banter and competitive streaks, and they assume this year will be the same.
So why are they suddenly enjoying nights holed up in their room together?
Bones can’t figure out what’s changed, why he likes being around Emil so much and why he’s suddenly falling asleep in Emil’s bed. And as far as Emil knows, Bones is straight, so why does he seem jealous when Emil arranges a random hookup, then asks all sorts of questions about what it’s like to kiss another guy?
To put an end to his roommate’s endless queries, Emil kisses Bones, convinced he’s just goofing around. But one encounter leads to another, until Emil begins seeing Bones in a different light. Underneath the clueless, carefree facade lies a deeper emotional underpinning that allows Emil to become more vulnerable too—and maybe even admit that spending time with his roommate is the best part of his day.

Still, Emil isn’t about to become another jock’s experiment, so he makes it clear that their hookups are totally casual. Until they’re not.