Preheat oven to 180°C. Place tomatoes on a large baking tray with garlic, herbs, oil and balsamic. Sprinkle with sugar, season with salt and pepper, then toss to coat. Turn tomatoes cut-side up, then roast for 1 hour or until tomatoes and garlic are softened. Cool, then peel tomatoes and garlic (the skin will slip off easily). Discard herb stalks. Whiz in a processor or blender to a coarse puree, then adjust seasoning.