Pre-heat the oven to 200°C.
Pour the tinned tomatoes into the bottom of the roasting dish. Add the fresh basil and balsamic vinegar, season with salt and pepper to taste and mix.
Arrange the sliced vegetables in rows, alternating between potato, courgette and red onion.
Spray the tops of the vegetables with low calorie cooking spray and sprinkle over the garlic and rosemary.
Cover the top loosely with foil and place into the middle of a hot oven for 45 minutes.
After 45 minutes remove the foil and place back in the oven for 15 minutes. When cooked the potatoes should have softened, but still retain their shape. There should also be a light golden colour to the top of the vegetables.
Remove from the oven and sprinkle over some optional extra fresh basil to serve.