Cloudflare - Recommended settings

You don't have to make any changes in the Cloudflare settings when using WP Rocket. If you want to be sure that there won't be any issues, you can either turn on the  Optimal Settings option on the WP Rocket Cloudflare Add-on, or you can manually proceed as follows:

Disable Rocket Loader

This feature is not related to the WP Rocket plugin and may instead cause problems. You can disable Rocket Loader from the Speed tab, just like this:

Enable Auto Minify for JavaScript, CSS and HTML

You can also do this from the Speed tab and it should look like this:

Incompatibility:
FacetWP relies on comments as part of their frontend functionalities - reference. Make sure that the HTML (Auto Minify) is unchecked to allow comments to be preserved by Cloudflare.
The same applies to any script relying on comments to inject content or manipulate the DOM. 

Set the Browser Cache Expiration to “1 year”

You can find this Cloudflare feature by following the guide at : Edge Cache TTL. Then, simply set the value to “1 year”, like this:

The TTL should be set to one year to prevent browser caching warnings in PageSpeed.

Set the Caching Level to "Standard"

This is very simple and it can be done in the Cache tab, like this:

Turning on the Optimal Settings option on the WP Rocket Cloudflare Add-on is what sets the recommended settings for you; this is what that setting should do on the Cloudflare side:

• Set Caching Level to "Standard".
• Enable Auto Minify for JavaScript, CSS and HTML.
• Disable Rocket Loader to prevent conflicts.
• Set Browser Cache Expiration to "1 year".