Heat oven to 375°F. Lightly oil a 9x13-inch baking dish.
Boil rigatoni in salted water until very al dente, 2 minutes shy of package time. Drain.
Warm olive oil in a large skillet over medium-high heat. Brown the beef, breaking it up.
Stir in onion and cook until softened, about 4 minutes. Add garlic and cook 30 seconds.
Add marinara, tomato paste, beef broth, Italian seasoning, red pepper, sugar, salt, and pepper.
Simmer the sauce until slightly thickened, 5 to 8 minutes. Remove from heat.
Toss the drained pasta with the meat sauce. Fold in half the mozzarella and 1/4 cup Parmesan.
Spread half the pasta in the dish. Dollop ricotta over. Top with remaining pasta.
Sprinkle the remaining mozzarella and Parmesan over the top.
Bake until bubbly and lightly browned, 20 to 25 minutes. Rest 10 minutes.
Scatter parsley over the casserole and serve warm.