multiple-roles.php

<?php
	$key = $wpdb->get_blog_prefix( get_current_blog_id() ) . 'capabilities';

	// Setup new meta query for user Roles
	$meta_query = array(
		'relation' => 'OR',
		array(
			'key' => $key,
			'value' => 'administrator',
			'compare' => 'LIKE'
		),
		array(
			'key' => $key,
			'value' => 'editor',
			'compare' => 'LIKE'
		),
		array(
			'key' => $key,
			'value' => 'author',
			'compare' => 'LIKE'
		)
	);
	
	$users = get_users( array( 'meta_query' => $meta_query ) );