I put mine under the house and just leave em, that simple. The life of the plant is stored in the rhizome and as long as it doesn't freeze, it should be fine. If your storing them in the garage, wrap the roots in a trash bag and keep them in the dark. Maybe try a cardboard box if you don't have anywhere to store them. When they are dormant they need no light and no water, that is if stored bare root. I'd pot up your small ones and put the rest under the the house or in the basement/garage. They are tougher than you think.
