Preheat oven to 400 degrees. Heat a large ovenproof gratin dish or skillet in the oven 15 minutes. Combine salt, pepper, thyme, and rosemary in a small bowl.
Toss potatoes in a medium bowl with the olive oil. Sprinkle generously with seasoned-salt mixture, and arrange potatoes in a single layer in preheated pan. Roast until they are golden on the outside and tender when pierced with a sharp knife, 25 to 30 minutes. Remove from oven, and serve hot with additional seasoned salt on the side.