For filling, in a medium skillet cook onion and garlic in 1 teaspoon hot butter over medium heat about 3 minutes or until onion is tender.
Meanwhile, in a food processor combine the 2 tablespoons parsley and 1 teaspoon of the rosemary. Cover and pulse until mixture is finely chopped. Add pumpkin, 1/4 cup Parmesan cheese, the onion mixture, 1/8 teaspoon of the salt, and the pepper. Cover and pulse until just combined.
Working with 2 wonton wrappers at a time, top each wrapper with a scant tablespoon of the filling. Brush edges of wrappers with water; fold one corner over filling to meet the opposite corner, forming triangles. Press down around filling to force out any air and to seal edges well. Cover filled ravioli with a dry kitchen towel while filling remaining wrappers.
For sauce, in a large skillet heat the remaining 3 tablespoons butter over medium heat. Stir the remaining 1/8 teaspoon salt and the flour into the butter; cook and stir 1 minute. Add the milk all at once; cook and stir until mixture is thickened and bubbly. Cook 1 minute more. Remove from heat; stir in the remaining 1/4 teaspoon rosemary. Cover and keep warm.
Cook ravioli in gently boiling water 2 to 3 minutes or until tender, gently stirring occasionally. Using a slotted spoon, transfer ravioli to serving plates. Spoon sauce over ravioli. Sprinkle remaining 2 tablespoons Parmesan cheese, and, if desired, toasted almonds, additional parsley, and freshly grated nutmeg.