Roast the Squash & Sausage: Preheat the oven to 425°F. Add the diced butternut squash, diced onions, and raw sweet Italian sausage to a large, sturdy, rimmed sheet pan. Break the sausage into bite-sized crumbles. Drizzle everything with avocado oil. Season the squash with salt, pepper, and garlic powder. Spread everything into an even layer. Place the sheet pan on the bottom oven rack and roast for 17 minutes, until the sausage begins to brown and the squash develops caramelized edges.
Deglaze & Build the Sauce: Carefully remove the sheet pan from the oven and place it over a burner set to low heat, provided your sheet pan is stovetop-safe. Push the sausage, squash, and onions toward the sides of the pan, creating an open space in the center. Pour in the white wine and beef broth, scraping up any browned bits from the bottom of the pan. Add the Dijon mustard, heavy cream, and balsamic vinegar. Stir everything together to create a creamy, savory sauce. Add the sprig of thyme or sage to infuse the sauce.
Add the Ravioli: Arrange the refrigerated ravioli directly in the center of the pan, nestling them into the sauce. Let the ravioli sit in the warm sauce over low heat for approximately 2 minutes to begin absorbing the flavors. Gently toss everything together, coating the ravioli with the creamy sauce and distributing the sausage, squash, and onions throughout the pan.
Finish in the Oven: Reduce the oven temperature to 375°F. Sprinkle the Parmesan evenly over the ravioli and sausage mixture. Finish with a light drizzle of balsamic vinegar and a spritz of avocado oil. Return the sheet pan to the oven and bake for 7–10 minutes, until the ravioli are tender, the sauce has thickened slightly, and the Parmesan is melted. Check that the sausage reaches 160°F for pork or 165°F for chicken.
Serve: Remove the thyme or sage sprig. Let the pan rest for 2 minutes to allow the sauce to thicken slightly before serving. Finish with additional Parmesan and freshly cracked black pepper, if desired. Serve warm, directly from the sheet pan!