There are a lot of people that keep roots from one season to the next-usually hoping the price will be better next year.Your roots should be fine to sell and I dont think they really dry much if any more after they are dried.
Just be careful with your states laws. Here in Ohio you cant hold it over without it being certified by the state. I'm not saying the dealer would be able to tell the difference, but in Ohio the dealers are supposed to ask a number of questions. Some of those questions I think is weather it was dug this year, What county it was harvested in, private or public land? etc.