I seldom use a campground when getting to a place, preferring to dry camp. I have stayed at campgrounds coming and going. You can get into these places with a big rig, but not very far. Which is okay of course since you are going to ride anyhow. Plenty far from the highway though. I have towed a 5th wheel in there pretty far and a big Lance pick-up camper. There use to be a campground 20 or so miles south of Lander. The highway north from Rawlins 287 (?) leads to Muddy Flats where you go east through Jeffrey City eventually getting to "T" intersection, which north takes you to Lander and south takes to to the BLM lands. Anyhow, at that intersection or very close to it there is a campground I have stayed at a few time. I have however showed up there twice when it wasn't open. Plenty of campgrounds close to Lander but there would be a tow to off road areas.
I seem to recall you need a Wyoming ORV Pass and it wasn't very expensive. I know that locals drive their ORV on the highways and byways but I couldn't tell you what that requires. I will tell you the Law enforcement in Wy are simply the best. They don't sweat the small stuff and bad guys would rather tangle with King Kong.
Be sure to bring bino's and cameras. Interesting critters all over the place. There are wolves and bears there so prepare accordingly. By the way, it is a long way between fuel/gas stations everywhere in Cowboy State.
s/f Steve