@ Mouliet Loads of people have had sex with someone they didn't mean to when they were upset/drunk/just been rejected/for revenge and for a whole host of other reasons. It's not the best idea you'll ever have but it's not a horrible thing to do and it certainly doesn't make you a horrible person. And I agree with Red Hood that your room mate did take advantage of you a bit what with the whole just been rejected/bawling your eyes out thing.
Is the roommate the one who told you to kill yourself? Even if it isn't, that's just messed up. I don't know the full situation, but you were vulnerable at the time and your roommate should not have taken advantage of you like that.