Preheat oven to 425 degrees Fahrenheit.
Place potatoes in a large baking dish or roasting pan. Add oil, duck fat, garlic, herbs, salt and freshly ground pepper. The potatoes should just be covered with fat/oil, if not add a little more olive oil. Place pan in the oven and allow to roast for about 40 minutes or until cooked through (potatoes will be easily pierced with a paring knife). Remove potatoes from oil and keep warm until ready to serve.