If you are going to evict your roommate, the unique situation can determine how much time you should allow for the departure. Most states require a 30 day notice in the event of an eviction. There are other options to try before the eviction.
Too Close for Comfort
If you feel as though you no longer need the extra financial help and want to no longer have a roommate, be upfront with them. If they have already paid the current month’s rent, refund it to them and they can use that money to ensure a new rental. If they know why you are wanting them to leave, the transition might go a bit smoother.
No Money Coming in
If you are paying your half of everything, your roommate is not and you are both on the lease, than the landlord would have to be the one to possibly evict the roommate. If you tell him about the situation and can show who is and who is not paying the rent, than he would probably begin a 30 day eviction notice against the non-paying tenant.
If You Are Fearful of Roommate
If your roommate has been physically abusive to you, or has made verbal threats against you, a restraining order is an option. Have the eviction notice served to the roommate and also file a restraining order against the roommate. This will ensure that the roommate is not allowed to be within a certain distance of you, including in the housing unit. This will just be temporary though, as the restraining order only lasts about two weeks. Going back to court will help ensure the issuing of a second order. It might also be a good idea to stay at a friend’s house or with a relative until the roommate has been successfully evicted and no longer has access to the rental.
Every situation is different, but generally a 30 day notice of eviction is standard. Checking with a lawyer for your state’s laws regarding eviction and also hiring him to draw up the necessary paperwork for the eviction would help ensure that things on your end have been done legally and will protect you in case the roommate takes you to court for unlawful eviction.