Preheat oven to 375°.
Combine sweet potato, parsnip, carrot, 2 tablespoons vinegar, oil, and salt in a large bowl; toss well.
Arrange vegetable mixture in a single layer on a large foil-lined jelly-roll pan; bake at 375° for 30 minutes or until lightly browned, stirring occasionally. Set aside.
Cook pancetta in a Dutch oven over medium-high heat 8 minutes or until crisp. Remove from pan with a slotted spoon; set aside.
Add shallots and onion to drippings in pan; cook 15 minutes or until golden brown.
Add remaining 1 tablespoon vinegar, thyme, garlic, and pepper; cook 1 minute.
Add wine, scraping pan to loosen browned bits. Add pancetta, lentils, and 4 cups broth to pan.
Bring to a boil. Cover, reduce heat, and simmer 30 minutes. Add remaining 2 cups broth and roasted vegetables to pan, and simmer 15 minutes, uncovered.
Add chard, and cook 2 minutes or until wilted.