There has recently been a discussion on the Alacrity mailing list about how the original roller boom reefing system is supposed to look like. Apparently some boats have some kind of device with a handle that, when turned, rotates the boom and rolls the sail around it.
My own boat does not have this device. Instead the arrangement is the simplest possible. The boom sits on a pin that is round at the top but square at the bottom. The hole in the boom is square. Thus the boom cannot rotate when it sticks completely on the pin. In order to reef the sail you have to move the boom partially off the pin, roll the sail in and then stick it back. This can of course be a difficult enough task when at sea in a swell. I have myself only tried this once or twice, normally I use to reef the classic way with lines. However, I may try the roller some more as it has it's advantages. The reefed part of the sail is rolled tidily away for example. However, one disadvantage is that the boom drops lower at its aft end endangering the heads of everybody in the cockpit when tacking.