Can be dried and used to make Orris root powder... used as both a fixative and scent in perfumery...
And a flavoring in some 'exotic' cuisines and for syrups.
Orris root - Wikipedia, the free encyclopedia
Not really for actual eating though.
We always just left some dirt in the roots and put bundles into layers of wet newspaper in big grocery store paper bags... then stuck a "Free Iris" sign on them by the road when ours were overgrown.
Daylilies make a much nicer edible floral boarder... the flowers (VERY yummy IMO) and tubers on the roots are both edible.