Preheat the oven to 400ºF.
Toss the potato slices in a bowl with the oil, rosemary, salt, and pepper. Spread on a baking sheet in a single layer and bake for 15 to 20 minutes. Remove from the oven, and turn with a spatula.
Bake them until golden brown and crisp, for about 15 minutes longer. Remove from the oven and serve immediately.
Yield: 4 side servings