Preheat oven to 400 degrees F.
In a large roasting pan or baking sheet, spread the cubed potatoes evenly. Drizzle the olive oil over the potatoes, and season with salt and pepper. Remove stems from rosemary and sprinkle over the potatoes. Cover with foil and place in oven. Bake for 45 minutes, remove foil and bake for an additional 15 minutes and allow potatoes to brown.
Serve with your favorite meat or fish dish.