Our fifth wheel and truck camper have no special protection. Nor does the truck. The main highways are paved with gravel in construction zones only, through which we go slow. We also go slow when we're on the backroads (where there usually isn't any traffic).
We did have one of the overhead bunk windows get broken in the motorhome on one of our winter trips. Hills are gravelled in Yukon winters and flying rocks are common then. A semi-truck was climbing up the hill from Donjek River while we were going down the hill. It threw a rock that broke the overhead bunk window. Plywood and duct tape did the job until we got home.
Bugs wash off. While stopped at Haines Jct one trip, another traveller commented he felt bad for all the bugs he was killing. I told him we encourage tourists to kill insects...if it wasn't for all the tourists on the highway the bugs could be real bad!