Please, read the documentation, specially the Site command docs at the end you will find the "Nginx setup per site" section to know how to add custom nginx rules. WP Rocket does not make sense when you have FastCGI cache available in Webinoly.
Nowadays, top PaaS cloud providers all of them have the option to use SSH keys and disable password authentication. That's the best method to protect your server against that kind of attacks.
Regards.