Preheat the oven to 400 degrees. Place 3 pumpkin, halved and seeded, on a sheet pan and drizzle with the oil, sprinkle with salt and pepper then roast in the oven for about 30 minutes or until a fork easily pierces through the pumpkin.
Remove the pumpkin from the oven and scoop the pulp from the shell of the pumpkin to a food processor. Whiz the processor until pumpkin is fully pureèd. Remove 1 cup of the pureèd pumpkin to a small bowl and the remaining pureé in a medium bowl and set aside.
Add 4 eggs to the pumpkin puree in the medium-sized bowl.
For the pasta, add 2 of the eggs to the small bowl containing the 1 cup of pumpkin pureé. Whisk until combined.
In a food processor place 4 cups of flour, 4 teaspoons of semolina flour, salt, and nutmeg. Pulse for about 2 seconds just to combine. Add the pumpkin and egg mixture to the food processor and pulse a few times to combine. Add the remaining 2 eggs until a dough is formed. If the mixture is moist and sticks together nicely like a dough, turn the mixture onto a clean work surface sprinkled lightly with flour and semolina flour. If it is too dry, add a few drops of water. If it is too wet, add a little flour. This dough should not stick to your hands, but just barely not sticky.
Knead the dough by using the palm of your hands and push the dough away from you then fold it toward you. Rotate the dough and continue until dough is smooth. This will probably take about 10 minutes. Divide dough into 2 balls, wrap each ball with plastic wrap and rest for 30 minutes in the refrigerator.
For the white sauce, melt the butter in a large saucepan over medium-heat. Add the sage leaves to the butter and fry them until crisp. Be careful not to allow the butter to burn. Remove the leaves to a paper towel. Slowly sprinkle 1 cup of flour over the butter and stir until combined (this should take about 2 minutes). Whisk milk and cream into the pan and bring to a boil. Reduce to a simmer and cook until thick, about 20 minutes, stirring consistently to keep the mixture from burning. Season with salt, pepper, and nutmeg.
Remove one of the dough balls from the refrigerator and place on a lightly floured surface. With a rolling pin, roll the dough until it is at the most 1/16th of an inch. You should be able to see through it. Cut the pasta into sheets to fit your pan with a very sharp knife.
Grease a 13 x 9-inch lasagna pan or casserole with butter. Reduce the oven temperature to 375 degrees.
Ladle a thin layer of the cream sauce on the bottom of the casserole. Cover the sauce with lasagna noodles. Overlap the dough if necessary. Add another layer of sauce to cover the noodles, top with 1/6 of the mozzarella, and Parmesan cheeses. Repeat layering 5 times more, then ladle on the remaining sauce, and add the remaining purèe pumpkin (from the small bowl) randomly over the top of the casserole along with remaining cheeses.
Cover the lasagna loosely with foil for 20 minutes or until the top begins to brown. Remove from oven and allow to cool for about 10 minutes before serving.