There are several measure that can be taking to prevent ice damming on your roof in times of tremendous ice and snow. Yes, we had a non-winter, but that could be completely different next year.
If you are putting on a new roof, have the installer add a barrier over the felt (and under the shingles, before they are installed) at the edges of the roof near the gutters. The barrier material is about 3 feet wide and comes on a roll. It will prevent any water that is forced under the shingles from leaking into the walls and attic.
For an existing roof, you can buy heater coils of several different types that will prevent ice from forming. One type is placed in the bottom of the gutter and can be plugged into an outlet on the exterior of the house. Another type is more of a serpentine electric coil that lays on the shingles just above the gutter. In this instance, you would want to put the coil on the roof if there is a forecast of an extended snow or blizzard approaching. The most elegant installation would be an electric coil in the gutter plugged into a dedicated exterior outlet near the roofline that is controlled by a switch from inside the house. If the water flows freely through the gutter and drains to the ground without the downspouts and gutters filling with ice, ice damming will not occur. See my post in 2009 regarding the creation of ice dams and how they form.