Preheat oven to 425 degrees. Lightly oil a baking sheet. Combine the tomatoes, red pepper, and garlic on prepared baking sheet. Drizzle with 6 tablespoons oil. Sprinkle with salt and pepper; toss to combine. Roast until vegetables are soft, and brown around the edges, 45 to 50 minutes. Squeeze garlic pulp from skins; discard skins.
Transfer vegetables to the bowl of a food processor. Process until smooth.
Heat remaining 2 tablespoons oil in a medium saucepan over low heat. Add vegetable mixture, thyme, and vinegar and cook until heated through. Taste and adjust for seasoning.