1. Preheat oven to 400 degrees F. Lightly coat a large baking dish with cooking spray.
2. In a large mixing bowl, toss together the potatoes, garlic, olive oil, rosemary, salt, and pepper.
3. Arrange the potatoes in a single layer in the prepared baking dish. Cover with a lid or aluminum foil and bake for 25 minutes. Remove the lid or foil. Turn potatoes and bake uncovered until the potatoes are soft and slightly browned (20-25 minutes).
4. Toss potatoes with butter and parsley to serve.