Buy a snow rake at a hardware store. These rakes are sold in kits requiring assembly.
Shovel paths around the house to allow for easy access to the roof. Clear the spaces so you have very little chance of slipping. Make sure to wear heavy boots with good traction before beginning.
Stand on a secure object, such a ladder, placed on the cleared path. Rake the snow slowly off the roof. Start with the easy spots and gradually move to harder-to-reach regions. If necessary, combine two snow rakes to make one longer rake and extend your reach.
Remove snow from as many areas of the roof as possible. Do not overextend yourself when attempting to clear hard-to-reach areas.
Remove enough snow to lessen the weight on the roof. Remove even amounts of snow from each area of the roof.