Take a look at this snow-covered roof in Japan and watch what happens when a man strikes it with a big stick. I would imagine the guy filming this has done this before and provided the other man with the stick. While this seems to work fairly easily and safely with the deep snow on the roof it would be an entirely different matter if there was more ice involved. If you attempt to remove snow this way always be careful not to get caught under it when it falls off the roof.