Preheat the oven to 375 degrees F. Combine the first 5 ingredients in a small bowl. Cover and refrigerate until needed. Place the potatoes, oil, salt and pepper in an ovenproof skillet or shallow-side roasting pan. Roll the potatoes around to coat with the oil. Roast the potatoes 30 minutes then sprinkle with chilies and roast for another 15 minutes, or until tender in the middle and crispy on the outside. Arrange the potatoes on a platter with the bowl of mayonnaise alongside for dipping.