get current user's role

You can get a list of Roles from the GetRoles method. (From the link)

  string[] rolesArray;

  public void Page_Load()
  {
       RolePrincipal r = (RolePrincipal)User;
       rolesArray = r.GetRoles();
       ...//extra code
  }

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().

Simplemembership in MVC4:

Getting the User's role-

var role = System.Web.Security.Roles.GetRolesForUser().Single();

To check if the user belongs to a certain role-

if (User.IsInRole("External"))