Preheat oven to 425°F (220°C).
Pat the chicken dry with paper towels and place it in a roasting pan.
Mix butter, olive oil, garlic, thyme, rosemary, paprika, salt, and black pepper in a small bowl.
Rub the mixture all over the chicken and under the skin if possible.
Stuff the chicken cavity with lemon halves and onion pieces.
Arrange carrots and celery around the chicken in the roasting pan.
Roast the chicken for about 1 hour and 15 minutes until the skin turns golden and crispy.
Baste the chicken with pan juices halfway through cooking.
Ensure the internal temperature reaches 165°F (74°C).
Let the chicken rest for 10 minutes before carving and serving.