Pre-heat the oven to 375°F.
To peel the pumpkin, halve it, then scoop out the seeds. Cut it into wedges, carve the flesh away from the skin, then chop it into small, bite-size pieces. For butternut squash, cut the squash in half, separating the upper half from the bulbous bottom. Use a sharp vegetable peeler or paring knife to trim away the skin. Cut off the top stem and chop it into bite-size pieces, then halve the bulbous end, seed and chop. Lightly dress the pumpkin or squash in EVOO, salt, pepper and nutmeg.
Arrange the pumpkin or squash on a baking sheet or cooling rack over a baking sheet and roast for 35-40 minutes, until very tender. Puree half of it in a food processor until smooth; reserve the remainder in a dish. Toast the seeds and nuts in the oven for the last few minutes of roasting time.
Meanwhile, combine the stock, water and saffron threads. Bring to a boil, then reduce the heat to low and keep the liquids warm.
In a round-bottomed pan or skillet heat the remaining EVOO, two turns of the pan. Add the garlic and onions and soften for a few minutes; stir in the arborio rice and toast for a minute or two, then add the wine and let it absorb completely. Add the saffron stock in small batches of a few ladles at a time, stirring a minute or two for each addition of stock. Cook the liquids out and continue to add more a ladle or two at a time for 18 minutes. Stir in the butter, cheese and puree of squash.
Serve the risotto in shallow bowls topped with the roasted squash, nuts and parsley.