Preheat oven to 400 degrees. Spray a rimmed 18 by 13-inch baking sheet with non-stick cooking spray. Lightly dust with flour and shake out excess.
In a large mixing bowl toss potatoes with remaining olive oil. Add parmesan, and rosemary and season with salt and pepper (then more to taste if desired), toss to evenly distribute.
Bake in preheated oven until golden brown on bottom, about 30 minutes. Remove from oven, add garlic and toss (they may stick slightly so use a thin melt a spatula to lift from pan and rotate).
Return to oven and bake until tender and lightly browned, about 15 minutes longer. Sprinkle with parsley and serve immediately.