Bring 4 quarts water to boil. Preheat oven to 425ºF.
Cut potatoes into 1-inch cubes and blanch 2 minutes in boiling water. Remove and drain. Place on baking sheet and add garlic, rosemary and olive oil. Season with salt and fresh pepper and place in oven for 30 to 40 minutes, until golden-brown. Remove and serve immediately.