The little roots often dry out but I have more problems with rotting when I try to, kind of, seal things up. Little roots lost to drying is one thing. Big roots lost to rotting is something else!
My dahlias are in plastic bags - just like you get from the store. I'm worried about admitting this because people may see "plastic" and think that they are wrapped. They are not!
Dahlia roots are kind of heavy and those bags are nice and light. They are, however, completely filled with peat moss. The bags just help me get the peat and roots down and back up the basement stairs. And, it separates the different types of dahlias (as much as there is any effort in that regard).
The roots are nestled with peat completely surrounding them. The bags of peat & roots are set on the basement floor and the tops are left open. So, it really kind of amounts to about a 10" layer of peat moss all over the floor with thin plastic separating the roots. The peat is not covered with anything.
. . . just how i do it.
Steve