add_filter(
    'gform_custom_merge_tags',
    function ($merge_tags) {
        $merge_tags[] = array(
            'label' => 'User Role',
            'tag'   => '{user_role}',
        );

        return $merge_tags;
    }
);

add_filter(
    'gform_replace_merge_tags',
    function ( $text ) {
        if ( ! str_contains( $text, '{user_role}' ) ){
            return $text;
        }
        global $current_user;
        $values = $current_user->get( 'wp_capabilities' );

        $roles = [];
        foreach ($values as $role => $enabled){
            if ($enabled){
                $roles[] = $role;
            }
        }
        //if you would like to change the seperator of multiple roles change whats in between the single quotes in the line below
        $roles = implode(', ', $roles);
        return str_replace('{user_role}', $roles, $text);
    }
);