Preheat oven to 425°F. Line a large sheet pan with foil.
Toss sausage slices, peppers, zucchini, cherry tomatoes, and red onion with olive oil, garlic, Italian seasoning, salt, and pepper. Spread in an even layer on the sheet pan.
Roast for 20-25 minutes, flipping halfway through, until sausage is browned and vegetables are caramelized.
While the pan roasts, cook penne according to package directions. Drain and set aside.
Toss roasted sausage and vegetables with hot pasta directly on the sheet pan or in a large bowl. Add a splash of pasta water if needed.
Serve topped with Parmesan.