Don't Let Snow & Ice Build up on Your Roof

Ice and water shield correctly applied, will help a lot but it is water resistant, not water proof even if it is correctly applied.   If you have ice dams or icicles, water is probably pooling on your roof.

If water is pooling on your roof, you will eventually have a leak.  It is a simple law of physics.  The snow and ice needs to be manually removed to allow the water to flow off of the roof.

Insulating the roof with a closed cell foam insulation may solve the problem if you have enough space available to get the proper R value on the entire roof.

A hit or miss approach to solving the problem can actually make the situation worse.   Make certain that the company you hire knows what they are doing.  The solution can be complex.