function kanha_change_logout_url_by_user_roles() {

$current_user = wp_get_current_user();
$role_name = $current_user->roles[0];

$redirect_url = site_url();


if ( $role_name === 'administrator' ) {

wp_safe_redirect( $redirect_url.'/wp-admin');
exit;
}

if ( $role_name=== 'subscriber' ) {

wp_safe_redirect( $redirect_url );
exit;
}

}
add_action( 'wp_logout', 'kanha_change_logout_url_by_user_roles' );