zagreus on "Retrieve users and roles gives error"

I'm trying to retrieve users for a blog including their roles. When I use this, I now get an error. I'm pretty sure this worked previously before the 4.6 update.

$args = array(
            'blog_id' => get_current_blog_id(),
            'fields' => array('id', 'display_name', 'user_email', 'roles'));

        $users = get_users($args);

Here's the error I get:

WordPress database error Unknown column 'wp_users.roles' in 'field list' for query SELECT wp_users.id,wp_users.display_name,wp_users.user_email,wp_users.roles FROM wp_users INNER JOIN wp_usermeta ON ( wp_users.ID = wp_usermeta.user_id ) WHERE 1=1 AND (
  wp_usermeta.meta_key = 'wp_capabilities'
) ORDER BY user_login ASC  made by require('C:\MAMP\htdocs\web\wp\wp-blog-header.php'), wp, WP->main, WP->parse_request, do_action_ref_array, rest_api_loaded, WP_REST_Server->serve_request, WP_REST_Server->dispatch, Trainerous_Mobile_Public->{closure}, Trainerous_Mobile_Public->users_get, get_users, WP_User_Query->__construct, WP_User_Query->query

As always, any suggestions / help much appreciated.