I have a disagreement with my roommate. Can I apply to The Landlord and Tenant Board ?

The Residential Tenancies Act (RTA) governs the relationship between the landlord and the tenant or tenants. Roommates or other occupants who are guests of the tenant(s) do not have any rights or protections under the RTA and cannot apply to the LTB.

Source: www.sjto.gov.on.ca