Prehead oven to 450 degrees F with the oven rack in the lower third. Bring 6 quarts of salted water to a boil in a large saucepan. On the stovetop, in a large baking sheet with sides, heat the oil, garlic, and rosemary. Do not allow the garlic to brown. Meanwhile, boil the potatoes in the water for 1 minute. Remove the potatoes with a slotted spoon and place them on the baking sheet. Stir to coat with oil. Roast the potatoes, on the baking sheet, on the lower oven rack. Roast for 20 minutes and then carefully toss with a spatula. Roast another 10 minutes or until cooked through, brown, and crisp. Season with sea salt and freshly ground black pepper. This is excellent served with Parmesan Crusted Chicken and Green Beans Almondine.