Question-Can I use my roof mounted a/c in my stationary rv

If there is any way for air to circulate from outside it would work, the less air the less efficient it will be. If there is no outside air then I don't know where the exhaust fan will get air from, if there is a grate at the other end I would say your best bet is to hook up the fan for better efficiency. Don't see how it could be against the law but who knows.