In a pot, bring the stock, 2 cups water and the saffron to a low boil. Lower the heat and keep warm.
Meanwhile, in a large saucepan, heat the EVOO over medium-high heat. Stir in the pancetta for a minute or two. Add the pumpkin (or squash), celery, carrot, onion and garlic; season with salt, pepper and nutmeg. Partially cover and cook until the pumpkin is just softened, 6 to 7 minutes. Stir in the rice for 1 minute. Add the wine and cook to evaporate. Add the warm stock, stirring in a few ladlefuls at a time and allowing the liquid to evaporate before adding more; cook for 18 minutes from the first addition of stock.
Stir in the butter and cheese in the last minute of cooking. Serve the risotto in shallow bowls. Top with the sage.