Preheat your oven to 425°F (220°C) and prepare a large roasting pan.
Peel and chop the carrots, parsnips, and onion into 1-inch chunks, then place them in the bottom of the roasting pan.
Toss the vegetables with 1 tablespoon of olive oil, half of the salt, and half of the pepper.
Remove the giblets from the chicken, pat the skin completely dry with paper towels, and place it on top of the vegetables.
Stuff the chicken cavity with the lemon halves and smashed garlic cloves.
Rub the remaining olive oil over the chicken skin and season evenly with the remaining salt, pepper, rosemary, and thyme.
Roast for 60-75 minutes, or until the internal temperature of the thickest part of the thigh reaches 165°F.
Remove from the oven and let the chicken rest for 15 minutes before carving to keep the meat juicy.
Serve a 6-ounce portion of chicken (skin removed to maintain calorie targets) with a generous helping of the roasted root vegetables.