NEWBIE WITH A QUESTION ABOUT ROOF AC
Roof a/c only works when plugged in to electricity or when running generator. You can not run the generator when you are driving. The roof a/c takes a lot of power to start so you can't run much else if you are using the generator to operate it. So no, you can't use it when driving.
If the coach batteries are fairly new, you may want to have the solenoid checked before you replace the batteries.