When I see English like this on a Japanese product, I'm never sure of how savvy the promoters are about the meaning. Do they just name is "Rock'n Puff" because these are little rock-shaped nuggets or are they trying to imply that you should be snacking on these as you watch a heavy metal concert on DVD. Perhaps you could use them to pelt someone in pseudo-biblical-style punishment only without the actual death. Instead of bruises and blood, you'll just leave little brown chocolate smears all over them.
This snack, made by somewhat low-rent snack maker Cisco, has a cocoa puff in the center, bits of corn flake and a chocolate coating. Since my experiences with Cisco's products have not been stellar, I passed on actually buying it, but I did think the name warranted a photo and a word or two.