In a large saucepan, combine the roasted vegetables, 5 cups of chicken broth, and ¼ teaspoon each salt and pepper. Bring to a boil, reduce heat, and simmer, stirring occasionally, until the carrots are very soft, 10 to 15 minutes. Stir in the orange juice.
Working in batches, transfer the vegetable mixture to a blender and puree until smooth, adding more broth if necessary to reach the desired consistency. (Alternatively, use a handheld immersion blender in the saucepan.)
Meanwhile, heat broiler. Place the bread on a baking sheet and, dividing evenly, spread with the maple-mustard sauce. Top with the chicken, onion, and cheese and broil until the cheese is melted, 3 to 4 minutes. Top with the arugula and serve with the soup, sprinkled with the dill.
