I can help you with this, as I am a Property Manager. Has the roommate lived in the unit longer than a year? If so, you will have to provide him with a 60 day notice to move, otherwise if he was there less than a year, you only need to provide a 30 day notice to move. If he does not move after the date specified on the notice, then you will have to start the eviction process. If you email me, I can email you the 30 and/or 60 day notice that you will need to provide to him.
We always recommend you talk with a real estate attorney. In this case, someone that specializes in landlord/tenant law.
On Trulia, you have real estate agents, brokers and lenders. While some of us may have personal experience in this particular area, we could only lend advice based on our personal experiences. It is possible that one of the agents or brokers is a property manager also and may be able to help you.
Best of luck,
Mark & Kari Shea
Shea Real Estate
Serving Greater San Diego