I thought of doing that while in Florida but IMHO the MH is just to small of an area to spray toxic chemicals in. For me and the dogs.
I've had real good luck with being prudent with the Sevin sprinkled around the tires and hoses leading into the MH.
The only time I had that problem one time was when I stayed a month in one CG deep in the woods and put a few of my plastic storage tubs outside on the ground. Palmetto bugs live in the woods under leaves and such.
That's how I found out about those darn holes they put in them under the handles. :R I've since taped off all the holes on all my storage tubs.
To the OP in Georgia those flying roaches as you call them were probably June Bugs. They aren't real bright and slam into the sides of the RV's at night usually committing suicide!