I have a landlord who placed an ad on Craigslist to get a room mate for me. He did not ask my permission and my lease clearly states only myself is to live there. (He wanted it that way). Can he do this, and what legal rights do I have against this and what happens if he does it? Thank you. State of Florida.

No, he can't do this. If he tries to move someone else in with you then he will be in default of the lease. At that point you will have the right to terminate the lease and move to a new place. You may be able to sue him for your moving costs. If your new place is more rent then you may be able to sue him for the difference.