Toss frozen rice with herbs and spread into bottom of a 3-quart baking dish. Top with 1 cup of the Italian cheese blend.
Combine peppers, mushrooms, tomatoes and sausage in a large bowl. Whisk together vinegar, oil, salt and pepper in a small bowl. Toss with pepper mixture. Add to baking dish on top of rice. Cover and refrigerate overnight.
The next evening, remove casserole from refrigerator. Heat oven to 375°. Remove plastic from casserole; sprinkle dish with remaining Italian cheese blend and the Parmesan. Bake at 375° for 30 minutes. Reduce heat to 350°. Cover with foil and bake 30 minutes more. Serve warm.