Zombies have been set up throughout the girders of a construction site, and you need to get rid of them by smacking them with objects like wrecking balls and boards. To do so, use the mouse and click on a chain to cut it. Utilize physics to your advantage to clear each level; all the zombies need to be dead to move on, but it only takes the gentlest of taps to kill a zombie.
The above premise pretty much sums up the entire game. Rolling Fall doesn't pull out any game-changing shocks; you're cutting chains and squashing zombies all the way through. The game's relatively short, with only 30 main levels and 10 bonus levels, so this isn't necessarily a big problem. Since the bonus levels can only be unlocked by earning high scores, there's also incentive to improve.
All in all, this is a solid use of your time whenever you want to send some zombie heads a rolling. Rolling Fall isn't going to change the sport of zombie-slaying as we know it, but it's certainly an excellent half-hour or so of physics goodness.