get current user's role

A user can be in more than one role so you can't get the one role that the user is in, but you can easily get the list of roles a user is in.

You can use the Roles type to get the list of roles that the currently logged in user is in:

public ActionResult ShowUserRoles() {
    string[] roleNames = Roles.GetRolesForUser();
    return View(roleNames);
}

Or if you want to get the roles for an arbitrary user you can pass in the username when you call Roles.GetRolesForUser().