If roommates are listed on the lease, each roommate is considered a tenant and each one will be individually fully responsible for the total amount of the rent due to the landlord, unless the lease specifically states otherwise. If only one roommate is listed on the lease and the others have not signed the lease, only the roommate listed is considered the tenant. The others are considered subtenants. Only roommates who sign the lease are responsible for the full amount of the rent to the landlord. The roommates who signed may have some separate claims against their non-signing, non-paying roommates, but such claims would typically be covered by contract law rather than landlord tenant law.