To prepare a three cheese vegetable lasagne recipe, you'll first need to prepare the vegetable lasagna. Place the ricotta cheese, sausage, pepperoni, onion, and garlic into resealable plastic bag. Seal the bag and place it in the freezer for at least 30 minutes. Peel and slice the carrots and celery. Toss the vegetables with the cheese and onion mixture. Spread the mixture on the bottom of the baking dish. Pour the tomato sauce over the top and sprinkle with grated Parmesan cheese. Bake at 350? for 45 minutes or until heated through. Remove from the oven and let sit for 5 minutes before serving.