From Vegetarian Times- December 2000. Roasting vegetables adds a satisfying, bold flavor dimension to soup. Be sure to roast the vegetables long enough for the onions to get well done, as undercooking them will give the soup a raw flavor. Because roasting leaves a brown skin on the potatoes, the soup won’t be perfectly smooth when you puree it. But don’t worry: A few chunks in the soup contribute to the texture.