AspNet Identity 2 - how do I work with roles?

With membershipusers, I could do like this...

If isAdmin Then If Not Roles.GetRolesForUser(email).Contains("admin") Then Roles.AddUserToRole(email, "admin") End If Else If Roles.GetRolesForUser(email).Contains("admin") Then Roles.RemoveUserFromRole(email, "admin") End If End If
How do I do this with Identity 2?
Thanks