Step 1: Preheat your oven to 425°F (220°C). Pat the chicken completely dry inside and out with paper towels.
Step 2: In a small bowl, combine the softened butter, minced garlic, rosemary, thyme, salt, and pepper to create a herb butter paste.
Step 3: Gently loosen the skin over the breast and thighs. Spread half of the herb butter directly under the skin, and rub the remaining butter all over the outside of the chicken.
Step 4: Stuff the chicken cavity with the lemon halves and the halved head of garlic. Truss the legs with kitchen twine if desired.
Step 5: Place the chicken on a roasting rack in a pan. Drizzle with a little olive oil and sprinkle with an extra pinch of salt.
Step 6: Roast for 15 minutes at 425°F, then reduce the oven temperature to 375°F (190°C).
Step 7: Continue roasting for about 1 hour, or until the internal temperature reaches 165°F (74°C) in the thickest part of the thigh.
Step 8: Remove from the oven and let the chicken rest for 15 minutes before carving to allow the juices to redistribute.