protected function get_role_options($instance, $coursecontext) {
        global $DB;

        $roles = get_assignable_roles($coursecontext);
        $roles[0] = get_string('none');
        $roles = array_reverse($roles, true); // Descending default sortorder.
        if ($instance->id and !isset($roles[$instance->roleid])) {
            if ($role = $DB->get_record('role', array('id' => $instance->roleid))) {
                $roles = role_fix_names($roles, $coursecontext, ROLENAME_ALIAS, true);
                $roles[$instance->roleid] = role_get_name($role, $coursecontext);
            } else {
                $roles[$instance->roleid] = get_string('error');
            }
        }

        return $roles;
    }