Pure Wow offers up a great tip for adding immense flavor to your roasted veggie pan. You just drizzle some white vinegar for extra *pop* on them prior to roasting and watch the flavor intensify in the pan. It's a great tip; I've seen balsamic vinegar used occasionally but the beautiful thing about the white vinegar is that its own flavor is rather transparent and you'll just be left with the flavor of the veggies themselves - brilliant!
Tip for Roasted Veggies
Roasted Veggies with a Secret Ingredient (!)