Add other wp roles in event author dropdown

/*
 * This snippet will include other wp roles in event author dropdown
 */

function my_em_override_wp_dropdown_uses($output){
    global $post, $user_ID;
    if( in_array($post->post_type, array(EM_POST_TYPE_EVENT, EM_POST_TYPE_LOCATION,'event-recurring')) ){
		// return if this isn't the theme author override dropdown
		if (!preg_match('/post_author_override/', $output)) return $output;

		// return if we've already replaced the list (end recursion)
		if (preg_match ('/post_author_override_replaced/', $output)) return $output;

		// replacement call to wp_dropdown_users
		$output = wp_dropdown_users(array(
		  'echo' => 0,
				'name' => 'post_author_override_replaced',
				'selected' => empty($post->ID) ? $user_ID : $post->post_author,
				'include_selected' => trues
		));

		// put the original name back
		$output = preg_replace('/post_author_override_replaced/', 'post_author_override', $output);
	}
	return $output;
}
add_filter('wp_dropdown_users', 'my_em_override_wp_dropdown_uses');