Bring a large pot of salted water to a boil. Using a sharp knife, slit each sausage down the side. Remove meat and place in a large ovenproof skillet. Add butter and onion. Set over medium heat. Stir to keep meat crumbly and cook until no longer pink (about 5 min). Add tomatoes and red pepper. Cook and continue stirring for 3 minutes to soften tomatoes slightly.
Add pasta to boiling water and cook according to package directions or until al dente (about 8 min). Meanwhile, sprinkle flour, oregano and nutmeg over sausage mixture. Stir to combine. Gradually stir in milk. Stir until mixture boils and thickens (about 3 min). Stir in parsley, Ricotta and half the Parmesan. Remove from heat.
Preheat broiler. Drain pasta very well and stir into sausage mixture. Add pepper and salt if needed. Sprinkle with remaining Parmesan. Broil for a couple of minutes or until top is bubbly.
Nutrients per serving: 554 calories, 24 g fat, 57 g carbohydrates (3.6 g fibre), 606 mg sodium, 25 g protein