Preheat oven to 475°.
Place first 5 ingredients in a shallow roasting pan coated with cooking spray. Coat vegetables with cooking spray; toss well. Bake at 475° for 35 minutes or until browned, stirring occasionally. Cool slightly; coarsely chop.
Combine whipped cream cheese and next 3 ingredients in a medium bowl. Stir in roasted vegetables. Spoon into a 1- quart dish. Sprinkle with Parmesan cheese, and broil 2 minutes or until cheese is melted. Serve immediately with melba toast rounds.