The following applies unless you have an automatic transfer switch which senses whether you are on shore power or generator power
You may need to plug the shore power cable into the side of the generator accessible through an adjacent compartment. Turn off the roof Air Conditioner and other 120vac items before starting generator, let it run 5 minutes then turn roof AC back on.
PS: If you shut roof AC unit down with generator running, wait 10 minutes before attempting to turn roof AC unit back on.