add_action('after_setup_theme', 'hide_admin_bar');
 
function hide_admin_bar() { 
   if(!current_user_can('administrator') && !is_admin()) { 
      show_admin_bar(false); 
   }
}

function user_role_check($roles) {
/* VERIFICA SE L'UTENTE HA EFFETTUATO IL LOGIN */
   if (is_user_logged_in()) :
      $user = wp_get_current_user();
/* CONTROLLA I RUOLI */
      $rolesUser = $user->rol
      $matching = array_intersect($rolesUser, $roles);
      $resp = false;
   if (!empty($matching)) :
      $resp = true;
  endif;
     return $resp;
endif;
}

$roles = ['subscriber', 'contributor'];
if (user_role_check($roles)) :
  add_filter('show_admin_bar', '__return_false');
endif;