- Cook rigatoni according to package directions. Drain in colander and return to pot; keep warm.
- Meanwhile, cook sausages in large nonstick skillet over medium heat, breaking meat up with wooden spoon, until no longer pink, about 5 minutes. With slotted spoon, transfer sausages to medium bowl. Add mushrooms to skillet and cook, stirring, until browned and tender, about 4 minutes. Stir in garlic and cook, stirring, until fragrant, about 30 seconds longer.
- Whisk together milk and flour in glass measuring cup until smooth; stir into skillet along with peas, salt, and black pepper; bring to boil. Reduce heat and simmer until sauce is thickened and peas are tender, about 3 minutes. Return sausages to skillet along with roasted peppers and scallions; remove skillet from heat. Add sausage mixture and Parmesan to rigatoni; stir until mixed well.
- Per serving: about 2 cups
This hearty dish is easily doubled for larger gatherings. It can be prepared up to 2 hours ahead and left out at cool room temperature. For longer storage, spoon it into one or two baking dishes and refrigerate, covered, up to 2 days. To serve, reheat, covered, in a 300°F oven for about 30 minutes, or until heated through.