I know EXACTLY how you feel.
And your roomates probably gave you a hard time about it, right? And when they come home tonight they will probably go on and on about how fun it was and they will talk about it for the next several days just to make you feel bad.
BEEN there HATED that. MOVED ON and LOVE IT!!!
Take it from me, ignore them, move on, and think about the healthy new you that you and you only are responsible for. You'll feel so much better for the rest of your life than one night on the town regretting decisions your bound to make. Keep focused and stay positive!