Preheat a roasting pan in a 350F (180C) oven. Add olive oil and pancetta; return to oven until pancetta is crispy. Push to one side and add herbs.
Put tomatoes into roasting pan, core hole down. Return to oven until tomato skins blister, about 5 minutes. Pinch off tomato skins. Toss carefully to keep tomatoes from falling apart.
Drizzle sausage with olive oil and rub in well. Place sausages into pan, pushing down amongst the tomatoes. Toss in garlic cloves. Sprinkle with salt and pepper. Return pan to oven for 1 hour, turning sausages once or twice.
Serve with crusty Italian bread, polenta or rice. Drizzle with a little high-quality balsamic vinegar.