You will have to serve a written 30 day notice of termination that includes a full calendar month. The notice has to be served by a process server. If the roommate does not voluntarily vacate when the notice expires you will have to commence a holdover proceeding against the roommate and his girlfriend.
Receiving a 30-day notice of termination shortly after reporting issues with the apartment could raise some concerns about whether the notice was retaliatory. California law protects tenants from eviction if it's in retaliation for exercising their rights, such as requesting repairs or reporting unsafe living ...