Our plugin works fine with WP-Rocket. Please, go to the menu option “Calculated Fields Form > Troubleshoots Area & General Settings”, tick the checkbox: “There is an active optimization plugin in WordPress” and then press the “Update” button.
As a second alternative, you can insert the form’s shortcode with the iframe attribute. For example, assuming your form’s id=1:
[CP_CALCULATED_FIELDS id="1" iframe="1"]