You should already have your squash roasted when starting this recipe. Use a fork to remove the strands of squash from the shells and into a large bowl, if you haven't already done so, then set aside.

Preheat the oven to 350°F. Grease an 8x8" baking dish and set aside.

In a large skillet, heat the oil over medium heat. Once hot, add the onions and cook until they are translucent, about 3-5 minutes. Add the garlic and cook just a minute or so more, until fragrant.

Add the ground sausage and cook until browned, breaking it apart as you cook. Drain any grease, if necessary.

Add the seasonings and the marinara sauce to the skillet. Allow to come to a simmer and let simmer for 5 or so minutes, then remove from heat.

Pour half of the sauce and meat mixture onto the bottom of the prepared baking dish and spread it evenly across the bottom. Then spread half of the spaghetti squash over the top of the sauce.

Spread 3/4 cup of the ricotta cheese over the squash, then sprinkle 1/2 cup of the mozzarella and 1/4 cup of the parmesan cheese over the ricotta.

Spread the remaining sauce and meat mixture over the cheeses and then top with the remaining squash. Repeat the layering of the remaining cheeses.

Cover loosely with foil and bake for 20 minutes. Then, uncover and bake an additional 10 minutes. To brown the cheese more, switch the oven to broil after the 10 minutes are up and broil until the cheese is golden, about 2-3 minutes. Once done, sprinkle with the chopped parsley and serve immediately. Refrigerate any leftovers.