Bring a large pot of salted water to a boil and cook the rotini until al dente according to the package directions. Reserve ½ cup pasta water, then drain.
Heat olive oil in a large skillet over medium-high heat.
Add the diced onion and cook for about 3–4 minutes until softened.
Stir in the garlic and cook for another 30 seconds.
Add the ground beef and cook until browned, breaking it apart as it cooks. Drain excess grease if necessary.
Stir in the Italian seasoning, paprika, crushed red pepper, black pepper, and a pinch of salt.
Pour in the marinara sauce and beef broth. Stir well and let the sauce simmer for 5–7 minutes.
Add the cooked rotini to the skillet and toss until the pasta is evenly coated.
Stir in the grated Parmesan until melted into the sauce.
Remove from the heat and sprinkle with fresh parsley or basil.
Serve immediately with extra Parmesan cheese if desired.