I would be careful with Roomsters, it is hard to tell with them what is legit and what is just a marketing strategy to get money from you. A lot of the times they will send a link that takes you straight to their website to sign up. I believe it requires a monthly payment from you to find a roommate which should not be the case. A lot of the times it sounds too good to be true. And as you can see from the comments from Roomster Representatives they are very strong-minded when people accuse them of being spam and take offense....that should tell you something. I will leave that judgment up to you.
I would recommend craigslist, although it may seem a bit scary but you just have to be careful when contacting people. Always meet in a public place, if they ask for too much information it's better to avoid them. If you have doubts about a posting then skip to the next. But most likely you will find something good through craigslist than Roomster.
Hopefully this helps and good luck on your search!