Preheat the oven to 400°F and place a shallow baking pan in the oven. In a large bowl, toss the potatoes with the olive oil until coated. Sprinkle with rosemary, salt and pepper; stir to combine well.
When the oven is hot, carefully remove the baking pan and spread the potatoes in an even layer. Return the pan to the oven and roast, undisturbed, for 25 minutes or until nicely browned on one side. Use a metal spatula to turn the potatoes. (If they stick, let them continue cooking for a few more minutes, then try to turn again.) Roast for 10 to 15 minutes more or until golden and tender. Cool slightly.