Preheat the oven to 350 degrees F.
Spray a glass baking dish with cooking spray. Place the olive oil, garlic, rosemary and salt and pepper, to taste, in a large re-sealable plastic bag. Add the potatoes, seal and toss to coat evenly. Pour into the prepared baking dish. Roast the potatoes for about 30 to 40 minutes until crisp on the outside and tender on the inside.