Here is the section on roommates titled Rights and Responsibilities of Co-tenants in the "RESIDENTIAL TENANCY POLICY GUIDELINE"
Read it carefully because if you want to bring this to arbitration later, you will have had to follow the guidelines there.
Probably the most relevant section for you:
In a monthly or periodic tenancy, when a tenant serves the landlord with a written notice to end tenancy, the effective date of the notice must be at least one month after the landlord receives the notice and on the day before rent is due. If the tenant gives proper notice to end the tenancy, the tenancy agreement will end on the effective date of that notice and all tenants must move out, even where the notice has not been signed by all tenants. When a tenant has ended the tenancy by giving written notice, all co-tenants remain responsible for meeting the terms of the tenancy agreement until the effective date of the notice. Co-tenants wishing to remain in the rental unit after a notice to end the tenancy has been given should discuss the situation with the landlord. If the landlord agrees to the tenant staying, the landlord and tenant must enter into a new written tenancy agreement.