Preheat the oven to 355°F (180°C).
Spread pumpkin cubes on an oven tray. Drizzle with extra virgin olive oil, sprinkle with pepper and sage, and toss on the tray until the pumpkin is well coated. Place the tray in the oven and bake the pumpkin for 20-25 minutes.
While the pumpkin is baking, heat some extra virgin olive oil over medium heat in a skillet and sauté the onions until they soften. This should take around 4-5 minutes. Add the zucchini, season with salt and pepper, and continue cooking until they become tender, about 7-8 minutes.
Once the pumpkin is baked, mix half of it with the zucchini and onions in the skillet. Add the white wine and simmer for an additional 10 minutes.
Using a blender, puree the remaining half of the roasted pumpkin with the cream or milk until you achieve a smooth sauce consistency.
While the vegetables cook, bring a large pot of water to boil. Once boiling, salt the water and then add the pasta and cook to al dente according to the packet's instructions. Before draining, set aside a cup of the pasta water, then drain and return the pasta to the pot.
Pour the pumpkin sauce over the drained pasta, stirring to combine. Mix well and, if needed, adjust the sauce consistency with the reserved pasta water.
Grease an oven dish with butter. Cover the bottom of the dish with a layer of pasta with pumpkin cream. Add a portion of the skillet-cooked vegetables. Dot with mozzarella pieces and sprinkle some grated cheese over. Continue layering in this manner then finish with a breadcrumb sprinkle on top.
Bake in a preheated oven at 355°F (180°C) until the top becomes golden and crispy, roughly 15-20 minutes. Once done, allow it to rest for about 5 minutes before diving in.