AddToRole and IdentityRole is not part of the model for the current context

I’m using Identity 2.1 to handle the user roles in my asp.net application. So far so good, i created new context extending from IdentityDBContext, extending the IdentityUser and IdentityRole to add a couple of new fields. However, whenever im trying to add a user to a specific role using the UserManager im getting The entity type IdentityRole is not part of the model for the current context.. So there seem to be something wrong with the user-role relationship, here is my code so far for reference: