Brown beef and garlic in oil in Dutch oven, about 5 minutes. Drain fat. Stir in thyme, salt, pepper, broth. Cover; simmer 1 hour until tender.
Meanwhile, preheat oven to 450°F. To roast vegetables, cut all into uniform pieces. Toss thoroughly with olive oil and balsamic vingear. Spread vegetables in baking pan in single layer; do not overlap. Roast 25-35 minutes or until sweet potatoes are tender, tossing once or twice during cooking.
Bring stew to boiling. Stir in cornstarch mixture; cook, stirring, 2 minutes to slightly thicken. Stir in roasted vegetables and 1 teaspoon vinegar.