Preheat oven to 425°F (220°C).
Line a large, rimmed baking sheet with parchment paper.
Combine oil, salt, and pepper in bowl, then add vegetables, tossing to coat. Sprinkle vegetables in a single layer on sheet.
Roast, covered by a second baking sheet, for 25 minutes, shaking or stirring pan a few times, until vegetables are slightly tender. Remove cover, and roast uncovered for 30 minutes longer, stirring occasionally, or until vegetables are tender and golden.
In a large high walled pot, warm broth, beet juice, and caper juice, add bay leaf and simmer for 5 minutes; then after removing the leaf, slowly add roasted vegetables and using an immersion blender, chop/blend to remove chunks. Continue until all vegetables have been added to sauce, adding water or more broth to chosen consistency.