The plugin offer you with couple of ways to boost the speed of your website. However, its best part and what got my focus instantly is the way it deals with JS as well as CSS minifications. This feature is not new, and there are also lots of plugins that helps to enhance your JS as well as CSS code for much faster loading times. Nevertheless, it can be challenging and when done wrongly, can prevent your website from loading correctly.
I have also evaluated WP Rocket minification on a website with a rather complicated CSS, which is broken with other similar WordPress Plugins. WP Rocket was able to handle this complicated case without any issues. When cached, the minified CSS & JS files speed up the loading of your pages.
Another optimization given by WP Rocket is called Lazy Image Loading. Essentially, upon the initial loading, the pages only render visible images to the website visitors. If your website has a lot of pictures, it will be loaded only when the visitor scroll down to the bottom. The best demonstration for this technique is Facebook which reveal more and more posts as your scroll down.
Lastly, WP Rocket has this option to enable page caching for your WordPress site. If you enable this, the web pages will be saved into static html files and served to your visitors.