Bettas are more solitary fish, so he won't be bored without a tankmate. Just put the tank in an area of your dorm room where he can see you/your roommate, and he'll be a happy camper.
If you can upgrade to a slightly larger tank so that you can put a heater in there, that would be awesome. He'll really perk up then!
6.6g planted bookshelf tank -
6 black kuhli loaches, 1 mystery snail
Anubias nana, Java moss
2.5g planted -
2 horned nerite snails
Anubias barteri var. nana 'petite', marimo ball
And a few tropical community and cool water tanks.