Preheat the oven to Gas Mark 4 or 180 degrees.
In an ovenproof dish, add the potatoes and finely chopped rosemary, season, drizzle with oil and mix well.
Add the carrots, courgettes (chopped into semicircles), sausages and garlic infused oil and place in the oven.
Bake for 30 minutes (turning the sausages halfway).
Add the vine tomatoes to the top and place in the oven for a further 5-10 minutes. Check the sausages are cooked (particularly if using thick ones), then serve.