Asynchronously load JavaScript . Rocket Loader™ will automatically asynchronous load your JavaScript resources, resulting in earlier rendering of your page content. Rocket Loader handles both inline and external scripts, while maintaining order of execution. Cloudflare will detect incompatible browsers and disable Rocket Loader. 

For more information read our recent blog post on the latest version of Rocket Loader: Cloudflare

Rocket Loader can be enable on your Cloudflare settings for the domain by visiting the Speed section of your settings on Cloudflare and scrolling down to Rocket Loader.