If you have snow melt off your roof when it's below 30F it's not vented properly or not enough attic insulation or both.Trick for frozen gutters and downspouts?
Nothing should be melting off the roof when it's in the twenties.
Have a buddy in PA with a ridge vent on his roof, snow covers it, and it doesn't breathe and roof melts off causing ice dams in his gutters. He has to load them up with salt or ice melter to stop ice damming. I keep telling him to put those gable vents in but....
Look around the neighborhood, the roof with snow on it the longest is a healthy roof with good insulation.