Preheat oven to 400°F. In bottom of large roasting pan, mix together carrots, parsnip, celery root, fennel, turnip and 2 tablespoons of olive oil.
Pat chicken dry, stuff cavity with half of orange and lemon. Truss legs of chicken together with butcher twine. Place on top of vegetables in roasting pan, Rub all over with 1 tablespoon of olive oil and sprinkle with 3/4 of spice mix. Mix remaining oil and spice mix into root vegetables. Place root veg in bottom of roasting pan and place chicken on top. Squeeze remaining lemon and orange over top.
Place in oven and roast until internal temperature taken in the thickest part of leg reads 165oF, about 1 hour.
Serve family style or serve cut chicken over vegetables