In large roasting pan, toss together the green beans, 1 tablespoon olive oil, and the 1/2 teaspoon salt. Drizzle the water over. Roast, uncovered, in a 450 degree F oven for 20 to 25 minutes or until the beans are tender, stirring once or twice.
Meanwhile, in small bowl, whisk together the vinegar, mustard, sugar, pepper, and the 1/4 teaspoon salt. Whisk in 1 tablespoon olive oil. Stir in dill. Toss cooked beans with vinegar mixture. Serve warm or cooled to room temperature. Makes 8 to 10 side-dish servings.