Heat a large skillet over medium-high heat and add olive oil. Swirl to coat. Add the onion and sauté until translucent, about 5 minutes.
Add the sausage, red pepper and mushrooms and sauté until meat is cooked through about 5 minutes. Add the jar of sauce, broken lasagna noodles, water, and rosemary. Stir to combine.
Cover and turn heat down to medium-low. Cook for 20 minutes, stirring occasionally until the pasta is al dente. Remove the lid and add the ricotta, 2/3 of the cheese and the parsley and stir to combine. Top with remaining mozzarella and serve immediately.