Heat oven to 425° F. In a large bowl, combine tomatoes, garlic, olive oil, salt, thyme and pepper. Spread onto a large rimmed baking sheet and roast at 425° F for 30 to 35 minutes, stirring once.
Spoon tomato mixture and any accumulated liquid into a large soup pot. Add chicken broth and 1 cup water. Bring to a simmer; cook 10 minutes. Transfer in batches to a blender and puree until smooth. Return to pot and stir in half-and-half and balsamic vinegar. Cook 3 minutes until heated through (do not boil). Serve with focaccia, if desired.
