It will be a large amount of root to deal with, but a reasonable solution. I would pot it into an appropriate sized pot and keep it in your garage over the winter. Provide SOME moisture to keep the roots from desiccating but not enough to promote their rotting. If your soil is clay based I would wash it off before storing and store in a mix of mostly perlite, lots of air with just a little moisture. Al

I would not store it where it gets down to freezing temps. I'd dig it, pack it in some peat or wrap in newspapers and store it much like glads or cannas are in colder climates.

Sue

Here is a link that might be useful: Here you go...Winterize elephant ear