I understand that I can use claims to make statements about a user:
var claims = new List();
claims.Add(new Claim(ClaimTypes.Name, \"Peter\"));
This is already done for you by the framework. When user is logged in, all user roles are added as claims with claims type being ClaimTypes.Role and values are role name.
And when you execute IPrincipal.IsInRole("SuperAdmin") the framework actually checks if the claim with type ClaimTypes.Role and value SuperAdmin is present on the user.
So don't need to do anything special. Just add a user to a role.