Coat a 9 by 13-inch baking pan lightly with cooking spray.
Bring a large pot of water to a boil over medium heat. Add the pasta and cook for about 6 minutes. It should be a little less than al dente; it will finish cooking in the oven.
While the pasta is cooking, heat the canola oil in a large skillet over medium-high heat, add the onion and garlic and saute until slightly tender, about 3 minutes. Add the tomatoes and Italian seasoning and cook for another 5 minutes. Chop the reserved sausage and peppers and add them to the skillet to heat through. Taste and adjust the seasoning with salt and pepper, to taste.
Drain the pasta and add it to the prepared baking pan. Pour the tomato sauce over the pasta and sprinkle with the cheese. Bake until the cheese is melted and lightly browned, about 30 minutes. Remove from the oven and serve.