From the sounds of things, you have been paying rent for a time although you are not officially on the lease. In such a case, you are more than guest, lodger or licensee. You are in fact, a "subtenant" (and that makes your roommate the "sub-landlord"). Accordingly, since your roommate is the only one on the lease, they woud have to file for an "unlawful detainer" (i.e. eviction proceeding) in court. Accordingly, they will have to comply with all legal requirements in order to get you legally removed. This starts with giving you written notice (typically 30 days). If you fail to vacate by the date specified in the notice, that's when your roommate will need to file the unlawful detainer. When it is granted, you will either then have to leave the premises or you can be removed by a sheriff.In the meantime, if your roommate takes any "self-help" remedy (such as changing the locks, removing your belongings, etc). you could sue them for unlawful eviction. Further, if you are in fact an "official" tenant, the only way to have you legally removed from the premises is to have the landlord file for the unlawful detainer action. In this regard, you should be aware that having your name on the lease is not the only way that you may be considered to be a formal tenant. In addition to being on the lease, you may have achieved the status of a tenant if the landlord accepted rent from you directly or they put (or allowed you to put) your name on the mailbox/doorbell and/or if you rented the place together with your roommate and it was clear that you were both on equal footing.At this point, you should consult directly with an attorney who handles these type cases or a tenant's rights group. They can best advise as to your spedific situation.