A California roommate agreement defines an arrangement between people occupying the same residence. A California lease agreement allows a landlord of residential or commercial property to write a legally binding rental contract with a tenant.What do I include in a Roommate Agreement? A: In California, since your roommate is on the lease, he has similar rights to the unit as you do, which complicates the situation. We are open to what we call "Roommate Switch Application" where we can add, remove, or switch a roommate with a very simple process. Learn about your month-to-month tenant rights in California with the help of the Martinez Law Center. 714-442-9741. We created this community to make the process of finding a new home, tenant, or roommate, just that bit easier. Tomonth rental agreement, also called a tenancyatwill, has no end date. Instead, the lease automatically renews every month when the rent is paid. --THIS IS A SINGLE ROOM INSIDE A HOUSE FOR RENT.