Preheat the oven to 425°F (218°C). Lightly grease a roasting pan with olive oil and set aside.
Clean the chicken by rinsing under cold water if desired and pat thoroughly dry with paper towels; trim excess fat.
In a small bowl, whisk together the melted butter, 4 tablespoons olive oil, and the juice from the zested lemon.
Place the chicken in the prepared pan and pour the butter–oil mixture over it, using your hands or a spoon to work some under the skin and inside the cavity.
Season the inside and outside of the chicken generously with salt and freshly ground pepper, then sprinkle the chopped parsley over the exterior.
In a medium bowl, combine 4 tablespoons room-temperature butter, chopped rosemary, chopped thyme, lemon zest, minced garlic, and paprika (if using); stir until smooth.
Rub the garlic-herb butter all over the chicken, including under the skin where possible for maximum flavor.
Stuff the cavity with the halved garlic head, tied rosemary sprigs, thyme sprigs, and quartered lemon, then tie the legs together with kitchen string.
Place the chicken breast-side up in the roasting pan and roast in the preheated oven for about 1 hour 15–25 minutes (total cook time about 80 minutes), basting once halfway through.
Roast until the juices run clear when pierced between thigh and body and an instant-read thermometer inserted into the thickest part of the thigh reaches 165°F (74°C).
When the chicken is done, baste with pan juices, then broil on high for 2–3 minutes just until the skin is deeply golden—watch carefully to avoid burning.
Remove the chicken from the oven and let it rest 10–15 minutes before carving; drizzle with pan juices and serve with lemon wedges.