“Rolligon” is mentioned a few times in the novel. One mention is in chapter 9, about the site of the big secret construction project.
Nevertheless many people were there, during and after construction. Even Warden visited and my co-husband Greg showed him around. Warden went by mail rocket, commandeered for day, and his Cyborg was given coordinates and a radar beacon to home on—a spot in fact not far from site. But from there was necessary to travel by rolligon and our lorries were not like passenger buses from Endsville to Beluthihatchie in old days; they were cargo carriers, no ports for sightseeing and a ride so rough that a human cargo had to be strapped down. Warden wanted to ride up in cab but—sorry, Gospodin!—just space for wrangler and his helper and took both to keep her steady.
Three hours later he did not care about anything but getting home. He stayed one hour and was not interested in talk about purpose of all this drilling and value of resources uncovered.
Another is near the end of chapter 24 about the warship that attacked Hong Kong Luna.
I looked up from a long roll of paper. “Mike, these news stories and our message to F.N. all assume that we have won in Hong Kong. How sure are you?”
“Probability in excess of eighty-two percent.”
“Is that good enough to send these out?”
“Man, the probability that we will win there, if we haven't already, approaches certainty. That transport can't move; the others were dry, or nearly. There isn't that much monoatomic hydrogen in HKL; they would have to come here. Which means moving troops overland by rolligon—a rough trip with the Sun up even for Loonies—then defeat us when they get here. They can't. This assumes that that transport and its troops are no better armed than the others.”
It sounds like rolligon is some mode of transportation on the Moon, but I'd like to know in more detail. The word isn't in my large dictionary, so I suspect Heinlein made it up.