Preheat oven to 475°.
Combine first 4 ingredients in a large bowl; arrange in a single layer on a jelly-roll pan coated with cooking spray. Bake at 475° for 25 minutes or until tender, stirring after 15 minutes. Stir in basil, vinegar, and 1/8 teaspoon black pepper.
Preheat broiler. Place polenta slices on a baking sheet coated with cooking spray; sprinkle with salt and 1/8 teaspoon black pepper. Broil 7 minutes on each side or until lightly browned. Spoon roasted vegetables over polenta; sprinkle with cheese. Garnish with basil, if desired.