Preheat the oven to 200°
Combine the cherry tomatoes, onions, green peppers and celery. Add to medium-sized roasting pan.
Drizzle the vegetables with the balsamic vinegar and olive oil and season with salt and pepper. Toss it around to ensure the vegetables are coated evenly.
Wrap the garlic cloves in aluminum foil and place onto the pan.
Roast the vegetables and garlic in the oven for around 20 minutes, long enough for the balsamic vinegar to reduce and caramelize the onions.
Meanwhile bring a pot of salted water to the boil and cook the pasta until al dente. Follow the package instructions. I found that 4 cups of water was enough for 3 cups of pasta, but you may need to add more water if need be. Once the pasta is cooked, drain it, but keep at least ¾ of a cup of pasta water to the side.
Once the vegetables are cooked, take it out. Carefully unwrap the garlic parcels, be warned, they will be very hot. Mash them with a fork on the sheet pan, until they are soft and broken up.
Add the basil to the sheet pan and toss to combined with the garlic and vegetables.
Add the vegetables to the pasta, together with the ¾ cup of pasta water and stir with a wooden spoon until all the pasta is well covered with the balsamic mix.
Serve warm, sprinkled with Parmesan cheese. (Optional)