Bring a large pot of water to a boil. Add penne pasta, and cook until tender, about 10 minutes. Drain.
Place the Italian sausage links in a small skillet over medium heat. Cook, turning occasionally until firm and cooked through.
In a separate larger skillet, combine the red and green capsicum, mushrooms, and Italian dressing. Cook and stir until the vegetables are tender, about 5 minutes. Slice the Italian sausages into rounds, and stir into the vegetables. Continue to cook and stir for another 5 minutes.
To serve, place servings of pasta onto plates. Top with the sausage and vegetable mixture. Sprinkle liberally with Parmesan cheese.