Roomster.com ( = OnlineSublets.com = SubletsWorld.com ) are SCAM. roomster.com pretends to be individuals looking for roommates/tenants on sites like craigslist.org to lure people to contact them. Then they respond you with URL's like onlinesublets.com and subletsworld.com to see their pictures. Those sites redirect you to roomster.com. When you ask the house/apt owners which listings are their, they never replied.
Here are 2 examples happened to me. You can text the numbers listed below for proof. They will reply you with web addresses like below, ask you to sign up on the site.
1. 214-531-3070, onlinesublets.com
2. 512-595-0468, subletsworld.com
Roomster.com also use their fake services to rip off landlords.