Step 1: Preheat Oven : Preheat oven to 425°F (220°C). Prepare a large roasting pan or oven-safe skillet.
Step 2: Prepare the Chicken : Pat the chicken dry with paper towels. In a small bowl, mix smoked paprika, garlic powder, onion powder, dried thyme/rosemary, cayenne, salt, and black pepper. Rub the chicken all over with olive oil or melted butter, then massage the spice mixture evenly over the chicken, inside the cavity, and under the skin where possible. Squeeze lemon juice over the chicken and place garlic cloves inside the cavity.
Step 3: Prepare Root Vegetables : In a large bowl, toss carrots, potatoes, parsnips, and onion with olive oil, salt, pepper, smoked paprika, and herbs. Spread vegetables evenly in the roasting pan.
Step 4: Roast the Chicken and Vegetables : Place the chicken on a rack over the vegetables or directly on top of them. Roast in preheated oven for 1 hour to 1 hour 15 minutes, or until internal temperature of chicken reaches 165°F (74°C) in thickest part of the thigh. Halfway through roasting, baste chicken with pan juices and stir vegetables to coat.
Step 5: Rest and Carve : Remove chicken from oven and let rest for 10–15 minutes to retain juices. Carve chicken into pieces. Serve alongside roasted root vegetables.
Step 6: Serve : Garnish with fresh thyme or rosemary. Optional: drizzle pan juices over chicken and vegetables for extra flavor.