There were a lot of different flavors of ROKON built - early ones had a fairly finicky West-Bend two-stroke, but were very light weight. My understanding is that various US special ops units did operate them back in the 1970s and that they were eventually replaced with the KLRs because the extreme light weight, ultimate go-anywhere capability and float-ability was not as desirable as more speed, durability, and payload. I've also run across reference to the USFS using them.
They always looked like a stupid amount of fun to me...