Set the oven to 425 °F. You may either gently grease a roasting pan or an oven-safe cast-iron skillet (at least 10 inches) or line a large baking sheet with foil. In order to achieve uniform crispiness on the underside of the chicken, I also advise installing a fitting rack within the vessel of your choosing.

Verify that the chicken's neck and giblets have been removed and that the inside is spotless. After removing any extra skin or feathers, gently dry the chicken all over with a paper towel.

Spread a generous amount of salt and pepper over the exterior, underside, and interior of the chicken, then place it on top of the rack, breast side up, inside the baking dish.

Olive oil, minced garlic, 1/4 cup melted butter, lemon juice, and rosemary should all be combined in a small basin. Mix the ingredients carefully to fully incorporate them. Rub the mixture over the chicken with a pastry brush or your hands (using disposable gloves if you'd like). To ensure the mixture reaches all areas of the skin, softly work your fingers under the skin.

Use the remaining half of the lemon, the onion, the carrots, and the garlic head to stuff as much as possible into the chicken cavity; any extras may be distributed around the bird. Tie the chicken legs together with kitchen twine.

Put the chicken in the oven and roast it for thirty minutes, uncovered.

Lower the oven's setting to 350°F. Remove the chicken with caution and brush it with the last 1/4 cup of melted butter. After that, return the chicken to the oven and cook it for a further hour or until its internal temperature reaches 165°F.

After taking the chicken out of the oven, baste it once more with pan juices. Before slicing and serving, let the chicken rest for a minimum of 15 to 20 minutes. This makes the roast chicken very juicy by locking in the fluids. Serve warm, as desired, or with your preferred side dishes and pan juices.