Very interesting! I recently visited Death Valley National Park, where at a playa called "The Racetrack" rocks up to about breadbox size are apparently pushed along by the wind, when the fine clay silt that accumulates in the playa (dry lake) is wet and slick. It was extremely windy while we were there a few weeks ago, 50MPH and gusting higher, enough to push you off balance, and in one place, Ubehebe Crater, visitors were warned to set parking brakes to avoid having cars blown into others! The windblown rocks leave "skidmarks" or shallow furrows in the mud. These snow rollers are a similar phenomenon, evidently, and surprisingly not more common...