Roasting vegetables brings out their sweetness.
Preheat oven to 450F.
Snap off the tough ends of asparagus and, if desired, peel the stalks. Toss the asparagus with oil and season with salt and pepper. Spread the asparagus in a single layer in a shallow roasting pan or baking sheet with sides. (If the pan is not large enough, use two pans.) Roast until tender and browned, 10 to 15 minutes, shaking once during roasting. Sprinkle with balsamic vinegar and toss. Taste and adjust seasonings. Let cool to room temperature; serve within 2 hours.
Make Ahead Tip: Can be made up to 2 hours in advance.