Bring a large saucepan of lightly salted water to a boil. Add pasta and cook for 8 to 10 minutes or until al dente; drain.
In a large frypan over medium-high heat combine sausage, chicken, Cajun seasoning and sage. Cook until chicken is no longer pink and juices run clear; about 8 minutes. Remove meat from frypan with a slotted spoon and set aside.
Saute onion, celery, capsicum and garlic until tender. Remove from heat then stir in cooked meat and half the Alfredo sauce.
Lightly grease a 20x30cm baking dish. Cover bottom with 4 lasagne sheets. Spread with 1/2 of the meat mixture. Repeat layers and cover with a layer of lasagne sheets. Spread remaining Alfredo sauce over top. Top with mozzarella cheese and sprinkle with Parmesan cheese.
Bake in preheated oven for 1 hour. Let stand 15 minutes before serving.