WP Rocket + CDN + FacetWP Template

<?php

// Add to your (child) theme's functions.php
// @link https://docs.wp-rocket.me/article/90-getrocketcdnurl

add_filter( 'facetwp_render_output', function( $output, $params ) {
    if ( function_exists( 'get_rocket_cdn_url' ) ) {
        $html = $output['template'];
        $html = str_replace( get_home_url(), get_rocket_cdn_url( get_home_url() ), $html );
        $output['template'] = $html;
    }
    return $output;
}, 10, 2 );