Roomie is singing "One Night Stand" from Janis Joplin (probably my most favorite american rock singer of all time), and the song picked isn't random either, I don't think! After everything that's happened with Lillian, and after that dream she just had of Lillian being very, VERY close to her (too close!), Roomie's having a backwards reaction out of fear. Fear of commitment, or just fear of the unknown before her! 

The song One Night Stand is very much a song of her past self, who had no romantic attachment for anyone, and lived her sexual life through one night stands. 

--> This is a rerun of the finished webcomic Go Get a Roomie! You can find these two strips in the old archive >here<!