I have trouble with caladiums rotting and so I probably would have a similar problem with dahlias. I would invest in more if I knew how to save them over winter.

Christie, why dig them? Mine come back every year with just a shredded leaf mulch on them over winter. I store the cannas in their dirt in the garage or under the bench in the cold place in the greenhouse. This year I just lifted the whole root balls out of the 4 pots and am storing them all together in a huge pot. The colors will stay separated that way, I hope. The caladiums don't all make it, but I've read you can store them in perlite. I might try that this year.
Sunny

I very seldom lose any. I've dug, put in peat moss, and dirt. This year, I put in pots with dirt and put in garage. its unheated, but I put them next to the house wall. I sometimes lose a few. but I always have more ordered for spring. One of my vices I guess. I've ordered 45 pots also, to have then on the deck this spring--deer ate freely this year, on them in the garden.