I have been living in my apartment for 11 years now. I have always had 2 roommates. I now have a roommate that me and my other roommate want to get rid of. I am the only person that has ever been on a lease. When we pay rent, we each pay with our own checks to the landlord. Is there a way for me to get rid of this roommate without involving my landlord??

If you are the only one on the lease, then your roommates are YOUR tenants and your landlord is not involved.