Pack your spaghetti pie in a salad container with a little pot for the dressing that's perfect for the pesto.
Preheat the oven to 375°. In a large bowl, toss the spaghetti with the marinara. In a 10-inch ovenproof skillet, heat the oil over medium. Add the sausages and cook, breaking up the meat with a spoon, until browned, about 6 minutes. Using a slotted spoon, transfer the sausages to the bowl of spaghetti.
In a small bowl, whisk the eggs, 1/2 cup mozzarella, and 1/4 cup Parmesan. Mix into the spaghetti and transfer to the skillet. Stir the spaghetti over medium-high heat until heated through, about 5 minutes. Cover with foil and bake until set, 25 to 30 minutes. Top with the remaining 1/4 cup mozzarella. Bake, uncovered, until the cheese browns in spots, 10 to 15 minutes. Let cool in the skillet for about 15 minutes.
Run a knife around the edge of the skillet to release the spaghetti pie. Slide it onto a cutting board and cut into wedges. Top with the crushed red pepper, basil, and the remaining 1/4 cup Parmesan. Serve with the pesto.