Start by preheating the oven to 450° -

Mince the rosemary and stir it into the melted butter with the salt and garlic.

Using your fingers and your hand, gently lift the skin of the breast and legs. 

Spread the seasoned butter under the skin and all over the top. Make sure you cover the entire breast area. Place the whole rosemary sprigs inside the cavity.

Liberally salt the skin, then place the bird in a roasting pan with a rack. 

Roast for 30 to 40 minutes, basting occasionally with the dripping or a little more melted butter.

When the top is beautifully crisp, turn the heat down to 350° and continuing cooking for about an hour to an hour and a half. The internal temperature should be at least 165°. The juices should run out clear and there should be no pink or red anywhere, especially near the bone (raw chicken is a very bad idea).

When it reaches the full internal temperature, remove it from the oven and let it rest for about 10 minutes.

Move to a serving platter and carve by removing the legs and wings first, then each breast half. The breast halves can then be sliced and served.