Preheat the oven to 375 degrees F (190 degrees C). Spray a 9x13-inch baking dish with cooking spray.

Bring a large pot of lightly salted water to a boil. Cook spaghetti in boiling water, occasionally stirring, until halfway cooked through, about 6 minutes. Drain.

Stir provolone cheese blend, 1 jar Alfredo sauce, drained spaghetti, ricotta cheese, Parmesan cheese, and eggs together in a bowl. Pour into the prepared baking dish. Cover the dish with aluminum foil.

Bake in the preheated oven until hot and bubbling, 60 to 75 minutes. Remove foil from baking dish and top spaghetti with remaining Alfredo sauce.

Stir marinara sauce and meatballs together in a saucepan; bring to a simmer, reduce heat to medium-low, and cook until meatballs are heated through, 15 to 25 minutes. Spoon meatballs and marinara over baked spaghetti.