There are many different problems when it comes to the roof; having your roof drain freeze is one of them. By the time the snow on the roof melts from rising heat and makes its way down to the roof drain, it quickly freezes again. The drain is jammed with ice and when more snow on the roof melts, it has nowhere to go as the drain can no longer do its job. There are some solutions to the problem but you’ll want to do as little as possible to avoid damage to the roof.
You can salt your roof but you’ll have to do it often, as rock salt melts fast. Make sure to put the salt only around the drain, as the salt can do damage to your roof. It might help to use a plastic shovel to get rid of snow around the roof drain before salting around the drain box. Avoid salt with oxidizing agents in it.
Electrical roof de-icing cables dangle in loops down the roof and just over the edge and create a heated path for proper water drainage. There are panels available that will hide the cables from sight. This method is considered to be inexpensive and effective.
Chemical de-icer is poured from the drain to each corner of the roof. It will likely have to be done more than once to be effective in thawing through to your roof and opening up drainage paths. It is often considered to be unsafe for the environment, damaging plants and polluting rivers.
There are many companies out there that claim to have the ultimate in roof de-icing solutions. It’s worth doing research, asking around, and checking out reviews of each of these “miracle” products before purchasing.