Heat a medium saucepan set over medium heat. Add the butter to melt. Whisk in the flour and cook for 1 minute, whisking constantly. Slowly add the milk, about 1 cup at a time, whisking between additions until smooth. Add the garlic and reduce the heat to low to maintain a gentle simmer. Simmer for 20 minutes, stirring occasionally with a whisk. Whisk in 1/2 cup of the Parmesan, the nutmeg and 2 teaspoons salt. Remove about 1 1/2 cups of the sauce to a bowl and set aside. Whisk in the pumpkin puree to the first batch of sauce and set aside to cool slightly.
Place the bacon in a medium skillet set over medium heat. Cook the bacon, stirring often, until golden brown and crispy, 10 to 12 minutes. Remove the bacon to a medium bowl with a slotted spoon, then stir in the mozzarella, ricotta, the remaining 1/2 cup Parmesan, the red pepper flakes, orange zest and 3/4 teaspoon salt.
Preheat the broiler to high. Place one oven rack in the bottom third of the oven and another in the top third.
Ladle 1 1/2 cups of the pumpkin sauce on the bottom of a 9-by-13-inch baking pan and reserve the remaining for a later use.
Bring a large pot of salted water to a boil over high heat. Blanch the pasta sheets according to the par-cook method of package instructions, about 4 minutes. Remove the pasta from the water using tongs and lay out on a baking sheet to cool slightly. When cool enough to handle, start assembling the rolls. Working with a pasta sheet vertical to you, place a small amount of the ricotta mixture on the end of a pasta sheet closest to you. Using a small spoon, spread the mixture evenly about halfway down the noodle. Roll the pasta around the filling, finishing with the end farthest from you. Lay the roll in the prepared pan, seam-side down. Repeat for the remaining filling and pasta. You should end up with two rows of 6 rolls. Use the two sauces to make stripes on the pasta. Ladle one-third of the pumpkin sauce along the side of the pan covering about half of a row of rolls. Right next to it, ladle half of the white sauce, covering another half of a row of rolls. Repeat with the remaining pumpkin and white sauces, finishing with pumpkin (5 rows of sauce altogether).
Place the pan in the lower third of the oven and broil to warm through, 15 minutes. Move the pan to the top third of the oven and broil until the top begins to brown and the sauce is bubbling, 4 minutes. Garnish each roll with a fried sage leaf to serve.
To fry sage leaves, fill a small saucepan set over medium-high heat with 1-inch of oil. When the oil is hot, add the sage leaves, 4 at a time, and fry, flipping often until the bubbles around the leaves subside, about 20 seconds. Remove with a slotted spoon and drain on paper towels. Season with a pinch of salt.