laravel route filter to check user roles

I am building a restful api in laravel 4 where there are users with different types of permission. I want to restrict access to different routes depending on the user role (which is saved in the user table in db)

How would I do that? Here is what I have so far (it's not working so far).

filters.php

//allows backend api access depending on the user's role once they are logged in
Route::filter('role', function()
{ 
return Auth::user()->role;
}); 

routes.php

 Route::group(array('before' => 'role'), function($role) {
 if($role==1){
        Route::get('customer/retrieve/{id}', 'CustomerController@retrieve_single');
        Route::post('customer/create', 'CustomerController@create');
        Route::put('customer/update/{id}', 'CustomerController@update');
 }

    });

Is it possible that I'm writing the syntax wrong for a "group filter"?