The way our leases are set up in order to get out of it we have to find someone to re lease the room. So i do believe that they have to sign their own lease for a year. My lease isn't suppose to end in October which is when I took over a girls lease and signed my own lease.
Sub leases are hard. What are the particulars of your lease. Monthly lease, when does it end, is there a clause in your contract that says you MAY sublet?
What was the working in your craigslist listing?
Send me a copy of your contract and I will check it out if you like.