root has stomata too, firstly on new roots (succulents ones or "mini-roots").
what i know is that stomatas are just on the stem shoot zone putting the O2 inside the leaves for photosythesis process.
Look dude, light induces the formation of photynthetic tissues (i do the inverse of it on grapevine, when a plant is dead, i take the sarmiento of the next one and put it into the soil to make a new grapevine plant) that has chlorophyle.
If you see a cross section of a root it has ground tissue and vascular tissue with tiny roots :), last ones enters the nutrients and also oxygen.

pd: my english is not the best :P, i’m an Agronomy Engineering from Chile.