I picked up a few bags of Calcium Chloride the other day. It's easier on concrete as well. Landscape supply was $20 a bag. Rona was out of stock and theirs had been $30.Throwing NaCl on your roof is going to get expensive fast as you corrode everything. KCl is best and even CaCl is a better choice than nacl. People just hear salt and grab what they can.
Make your own hand warmers. Throw a half cup of the stuff into a plastic bag and add water or snow when you need heat. It's exothermic and gets very hot very fast.