Preheat oven to 350 F. In a sauce pan, add butter and melt then sprinkle flour over butter and stir for about 1 minute. Whisk in milk and pumpkin puree. Add salt, garlic powder and black pepper. Bring to a boil continously stirring for about 4-5 minutes or until sauce begins to thicken. Once sauce thickens remove from heat and mix in Parmesan cheese. Boil Lasagna noodles per package directions so they are al dente. Cook Sausage in a pan. In a 9 x 13 inch baking dish, Pour a thin layer of the pumpkin cream sauce on the bottom (about 1/4 cup). Lay down a layer of Lasagna noodles.  Followed by another thin layer of pumpkin sauce (this time about 1/2 cup). Dot spoonfuls of the ricotta cheese along the layer. Add 1/3 of your cooked sausage. Sprinkle a thin layer of mozzarella cheese. Lay down another layer of noodles and repeat all of the ingredients again. Continue layering until you run out of ingredients or you are a minimum of 1/2 inch from the top of your dish. The top layer should just be noodles followed by sauce, then Mozzarella and a sprinkle of Parmesan cheese. Bake for 30 minutes or until the mixture begins to bubble and cheese on top starts to get golden.