The next step in cooking a frozen turkey is to place the chopped vegetables in the bottom of the roasting pan. Add 2-3 cups of water to the pan. I find that when I'm cooking a frozen turkey, I need more water in the roasting pan than I do when I'm cooking a turkey that has been thawed. I assume this is because the turkey doesn't make many drippings during the first few hours of cooking, as it is still thawing in the oven.
Now place the turkey in the preheated 325-degree oven, and roast for 2-3 hours.