There is no THC in the root ball. The THC is the liquid inside the Trichomes, the part that turns cloudy at peak harvests and then turns amber as the quality degrades. In fact if you dry your weed that way you run a greater risk of mold due to the extra moisture that needs to be dried. Also wrapping the roots with a plastic bag, they will rot and mold before they dry out. I would think that some type of mold or poison from the rotting roots would find it way into the rest of the plant as it fights for survival looking for moisture to drink up.