I've actually been in a similar situation. My senior year of college, I needed to find a roommate to stay in the dorms, well more specifically the one I really wanted to live in. I was even willing to move in with some girls who had an ad up for needing a roommate for the university apartments, but that did not work out because I contacted them too late. So, I ended up going to housing sign ups all by myself and randomly placed with someone, but fortunately in the dorm I wanted to live in. It actually didn't turn out too bad either. The girl I got placed with actually was so much nicer and better than the girl I had been living with for 2 years before that, and we chose to live with each other. So yeah, sometimes random roommates turn out better than ones you planned.

I don't know how old you are, but if they are doing work placement living, it might not be so bad. More than likely you might end up with people with some common interests. If it is not so good though, at least try to find 1 person you can count on, so you don't go crazy.