A roasting pan is generally used to roast items on the stove or oven, such as turkey, vegetables, potatoes or chicken. Roasting pans can be a heavy tin foil and disposable or can be sturdy cooking pans found at department and specialty stores, designed for multiple uses. The main purpose of a roasting pan is that it can hold up under high heat. While roasting items is the pan's primary purpose, roasting pans can also be used in other recipes, including cooking lasagna.
Preheat the oven to 300 degrees Fahrenheit. Wait until the oven has fully heated before placing the lasagna in the oven to ensure it cooks properly.
Place a roasting pan on the counter. Grease the bottom of the pan thoroughly with a cooking spray or other form of grease, making sure to get all four sides and all the corners of the pan. Sprinkle a light layer of Parmesan cheese along the bottom and sides of the pan.
Fill with a lasagna, using a recipe of your choice.
Stop layering the noodles, sauce and cheese after the second layer. Measure the thickness of the lasagna by standing a ruler either inside the pan or next to the roasting pan. Do not add any more layers if the thickness of the lasagna is more than four inches because it will not cook evenly.
Place a lid on the roasting pan or cover the pan tightly with tin foil. If using foil, pinch the sides of the foil over the sides of the roasting pan, so a tight seal is formed. Place the pan in the oven, and bake the lasagna.
Check the lasagna every hour to see how it is baking. Add four to five tablespoons of tomato sauce if the lasagna appears to be drying out. Place a cooking thermometer in the middle of the lasagna to check the temperature in the center. Wait until the temperature is at least 165 degrees Fahrenheit, which takes between three and four hours.