Create a user role within a multisite that can add other users

Hi There,
I've added a couple of custom user roles to my multisite install. The role I've added is essentially an admin role, however I've given it it's own name as they have requested a white-label admin experience for all the sites on their account.

The issue I am having is that I can't seem to allow this user role to add new users (this seems to be just a function for admins and super admins) - is there a way to allow this for my new user role? Here is my code that creates the role:

add_role( 'fts_admin', 'FTS Admin', array(
            'delete_others_pages' => 'true',
            'delete_others_posts' => 'true',
            'delete_pages' => 'true',
            'delete_posts' => 'true',
            'delete_private_pages' => 'true',
            'delete_private_posts' => 'true',
            'delete_published_pages' => 'true',
            'delete_published_posts' => 'true',
            'edit_dashboard' => 'true',
            'edit_others_pages' => 'true',
            'edit_others_posts' => 'true',
            'edit_pages' => 'true',
            'edit_posts' => 'true',
            'edit_private_pages' => 'true',
            'edit_private_posts' => 'true',
            'edit_published_pages' => 'true',
            'edit_published_posts' => 'true',
            'edit_theme_options' => 'true',
            'export' => 'true',
            'import' => 'true',
            'list_users' => 'true',
            'add_users' => 'true',
            'create_users' => 'true',
            'delete_users' => 'true',
            'manage_categories' => 'true',
            'manage_links' => 'true',
            'manage_options' => 'true',
            'moderate_comments' => 'true',
            'publish_pages' => 'true',
            'publish_posts' => 'true',
            'read_private_pages' => 'true',
            'read_private_posts' => 'true',
            'read' => 'true',
            'remove_users' => 'true',
            'upload_files' => 'true',
            'manage_sites' => 'true',
            'manage_network_options' => 'true'
       ) );