WP Rocket is a premium caching program. The Beaver Builder team use and recommended. So do many others including Chris Lema who named it the best caching program for 2016 . WP Rocket do not run and affiliate scheme so you can be sure the recommendation are genuine.
I personally did not want to start paying another subscription and hoped WP rocket would not be good. That was about 2 years ago and I’ve been happy to pay since.
My personal recommendation is looking for free caching is WP Super Cache. A safe bet as it is looked after by Automattic and has history. In may experience it was more reliable that some of the other that do other thing but fail on some server or get poor support and updates.