1. Bring a large pot of salted water to a boil. Add pasta to boiling water and cook according to package directions or until al dente, about 8 min. Drain pasta very well. Set aside.
2. In a large and deep oven safe skillet or pot, over medium heat, break apart sausage meat until crumbly. Add onion and stir frequently cooking until sausage is no longer pink and onions have softened, about 5 min. Add tomatoes and bell peppers. Cook, stirring, for 3 min to soften tomatoes slightly.
3. 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.
4. Preheat broiler. Stir cooked pasta into sausage mixture. Add pepper and salt if needed. Sprinkle with remaining Parmesan. Broil for a couple of minutes or until top is bubbly.