Preheat oven to 450°F. Halve squash and remove seeds. Season with salt and pepper and place, flesh side down, on a baking sheet. Bake until tender and a knife comes out easily, about 40 minutes. Use a spoon to scoop out flesh; puree in a food processor or blender until smooth.
Melt 1 Tbsp. butter in a skillet. Add shallot and cook until tender, about 3 minutes. Add chopped sage, squash puree, ricotta and 1/4 cup Parmesan. Season with salt, pepper and nutmeg, and cook for 1 minute. Remove from heat and allow to cool completely.
Place one wonton wrapper on work surface, keeping the rest covered with a damp cloth. Brush wrapper with water and place 1 tsp. squash mixture in center. Place another wrapper on top and seal together with fingers, taking care to push out air bubbles. Use a 3-inch round cookie cutter to cut filled ravioli into circles. Keep finished ravioli covered while you work.
In a skillet over medium heat, fry pancetta until crispy, about 5 1/2 minutes. Remove from pan and drain on paper towels. Wipe skillet out.
Bring a large pot of salted water to a boil. Melt remaining butter in skillet over very low heat, then add sliced sage. Cook butter and sage until butter turns light golden brown, about 5 minutes; remove from heat. While butter is browning, add ravioli to boiling water, stirring gently so they don't stick together. Cook 4 minutes, then carefully drain.
Place 3 ravioli on each plate, top each with 1 Tbsp. browned butter and garnish with 1/2 Tbsp. Parmesan, some crumbled pancetta and one sage leaf. Serve hot.