1. Preheat the oven to 450 degrees.
2. Coat a baking sheet with vegetable cooking spray.
3. Wash and peel the potatoes.
4. Cut the potatoes into ½-inch cubes, and put them in a large bowl.
5. Put the oil, rosemary, and salt in a small bowl. Stir together.
6. Pour the oil mix over the potatoes. Stir to coat the potatoes evenly.
7. Spread the potatoes on the baking sheet.
8. Bake for 25 to 30 minutes, or until lightly browned.