"You can also use both Nginx FastCGI cache and WP Rocket’s page caching, though we don’t recommend this approach." (quoted from your link)
WordOps already has rules for WP Rocket to work if you use the flag --wprocket. I looked over the rules nginx-rocket and they are the same as those in WordOps, except nginx-rocket by SatelliteWP have some extra headers.
If you use WP Rocket, you don't need FastCGI Cache anymore. If there are static versions created by WP Rocket, will be served to visitors.