We do just the opposite with our roof vents and all windows when traveling .... keep them all closed.
We like as much as possible a dust free coach area in our Class C. The interior of a motorhome is a big area to keep clean as compared to the interior of a vehicle so to keep the motorhome dusting and vacuuming to a minimum before, during, and after travel we keep it all closed up when going down the road. Our Ford's cab ventilation system - when set to interior recirculation - can process a lot of warmed or cooled air in a hurry. Our entire 24 foot Class C can be maintained by this system in any weather with no outside air coming in to dirty things up.