Preheat oven to 375°F. Have ready a large roasting pan. Mix minced garlic, rosemary, salt and pepper in a small bowl; rub all over pork.
Put meat, bone side down, in pan. Cut about 1/4-inch off tops of whole heads of garlic and add with oil, rolling heads in oil to coat.
Roast uncovered, 1-1/4 hours or until an instant-read thermometer inserted in thickest part of roast (not touching bone) registers 155°F. Let rest 15 minutes (temperature of meat will rise to 160°F). Carve and serve with cloves of roasted garlic to squeeze from skins onto pork.