这是一个基本（未经测试）版本的代码，我认为可以解决您的问题：

<?php
/**
 * Redirect UnAuthorized Users from my page.
 * 
 * Users will be redirected to another page if not authorized.
 */
function wpse375662_redirect_unauth_users() {
    // Not that particular page - bail out.
    if ( ! is_page( $page_id ) ) {
        return;
    }

    // User has permission - bail out.
    if ( current_user_can( $user_role_here ) ) {
        return;
    }

    // Add URL parameter.
    $parameterized_url = add_query_arg( $your_custom_page_url, \'unauth\', true );

    // Redirect the user.
    wp_redirect( $parameterized_url, 302 );
    exit();
}

add_action( \'template_redirect\', \'wpse375662_redirect_unauth_users\' );

/**
 * Display a message upon redirection.
 */
function wpse375662_message_for_unauth_users() {
      if ( filter_input( INPUT_GET, \'unauth\', FILTER_VALIDATE_BOOLEAN ) ) {
            echo \'<div style="style="absolute; top: 300px; left: 50%; transform: translateX(-50%); z-index: 9999; padding: 2rem;" role="alert">You are not authorized to display the content of that page</div>\';
      }
}

add_action( \'wp_footer\', \'wpse375662_message_for_unauth_users\' );