I live in California , my roommates moved on February 05, 2010 without telling the landlord now that things went bad where they moved they want to come back and say everybody that was remaining at the house has to move out , the landlord said he's between a rock and a hard place does the landlord have to let them come back?

First its not a good idea to piggyback your question on someone else's. This can lead to confusion. You should start a new thread. So I've moved your question to its own thread.

If they moved without informing anyone, then they may still tenants and can move back. They will, of course, have to pay Feb's rent. However, if the landlord can prove then vacated and breached the lease, then he does not have to let them return. As for people moving out, they have no right to force anyone out unless they are occupying space they may be entitled to.

Were you under a lease? If so, when does the lease expire? Did the landlord move in replacements? Did they sign the lease? How many people are we talking about?