Ice dams happen with leaky roofs right? I used to roof rake until i had my attic insulated. I don't need to now except on tha back I have a flat section off the back of my house. I've been raking that. It's not the snow I'm worried about but its like you said. Snow and then rain.

I kind of think of roof raking to be important for low pitches or uninsulated attics. If you a have buttoned up attic and a normal pitched roof then I don't think you need to do anything.

If you have icicles, you should roof rake