Ladder and shovel is the only way. It is dangerous especially on a pitched roof. Do not attempt to wash it off, especially if you are worried about structural problems, the snow will absorb and freeze a lot of water adding a lot of weight before any snow is removed.
Look at your weather forecast, if it is going to be warming up above freezing a lot of the snow will be melting rather quickly.
Ice dams can be a problem, but they are not an immediate problem, they just put a lot of wear and tear on your roof over the years. If you are worried about ice dams clean the snow off your over hangs to minimize the problem. Some ice dams around vents can cause leaks, that only leak in the winter, those are a problem that need to be addressed in the summer time after the snow is gone by an expert, I suggest calling a pro or search in the DIY SE for a solution.
At any rate your problem is one of weighing the risks of getting up on the slippery roof against the risk of structural failure or injury from snow falling off the roof.
If you have enough room around the building you could devise a small plow on a long handle and pull the snow down. This will be easy on new snow fall that is rather light and fluffy, older snow falls that have packed down and become crusty may not be so easy.