Prepare pasta according to package directions; drain.
Heat the oil in a large nonstick skillet. Add the onion and bell pepper and cook until crisp-tender, 2 – 3 minutes. Add water and continue cooking, stirring occasionally, until the vegetables are tender, about 8 minutes. Add the sausage and cook, breaking it up with a wooden spoon, until browned, 6 – 8 minutes. Stir in the tomatoes, seasoned salt, and Italian seasoning; bring to a boil. Reduce the heat and simmer, covered, until the flavors are blended, about 15 minutes.
Preheat the oven to 375º. Spray a 1 1/2-quart casserole with nonstick spray.
Add the cooked pasta to the skillet, tossing well to combine. Spoon half the pasta mixture into the casserole. Sprinkle with 1/2 cup cheese. Spoon the remaining pasta mixture over top. Sprinkle with the remaining 1/2 cup cheese. Cover loosely with a tent of foil sprayed with nonstick spray. (Do not let foil touch cheese). Bake until the filling is hot and bubbly and the cheese is melted, 20 – 25 minutes. Let stand 5 minutes before serving.