The rolling stone it rolled and rolled, and it gathered no moss and gathered no gold, but it sang to itself as it rolled along just for the fun of hearing the song.
The rolling stone it rolled and rolled till it got too shiny and smooth to hold, and it laughed at the stones that were gathering moss, who were lumpy and bumpy and terribly cross.
Everyone knows the old saying that "a rolling stone gathers no moss," usually meant as a warning: keep moving and you'll end up with nothing to show for it. Here the saying gets turned upside down. The stone really does gather no moss and no gold, but it doesn't seem to mind. It rolls along singing, purely for the pleasure of hearing its own song.
The speaker sounds amused and fond, almost like someone telling a nursery rhyme. The bouncy rhythm and easy rhymes keep the mood playful and light. In the second stanza the stone gets the last laugh. Constant motion has made it smooth and shiny, while the stones that stayed put are "lumpy and bumpy and terribly cross." The poem quietly suggests that staying still isn't the same as being content. What the stone has is freedom, and a kind of happiness that doesn't depend on owning anything.