Peel the turnip and parsnip. Cut the both vegetables into fry shapes approximately ¼ inch thick.
Slice the radishes into thin rounds, approximately 1/8 inch thick.
Place the vegetables in a 9×13 glass baking dish. Add the oil and sprinkle the salt over the vegetables. Using your hands, toss the vegetables until evenly coated with the oil and salt.
Spread the vegetables out so the pieces are not touching. You may need a second 9×13 glass baking dish.
Bake for 10 minutes. Turn the pieces over with a spatula. Bake for an additional 10 minutes. When done, the parsnips and turnips should be tender and the radishes should be approaching translucent.