Preheat the oven to 200˚C/Fan 180˚C/Gas 6. Toss the tomatoes, garlic and 2 tbsps oil in a roasting tin; season. Remove the packaging and film from the sausages but leave in the foil tray. Put the roasting tin and foil tray in the oven for 15 minutes, giving each one a toss halfway through.
Heat the remaining 1 tbsp oil in a large non-stick frying pan and fry the courgettes with the pinch of salt for about 8 minutes, turning regularly until golden. In a separate pan of boiling water, simmer the pasta for 10-12 minutes then drain, reserving a cup of pasta water.
Remove the courgettes from the frying pan and set aside on a plate. Slice the sausages and add to the pan, frying for a couple of minutes, then tip in the pasta, tomatoes, any roasting juices, 2-3 tbsps pasta water and the courgettes. Toss together briefly and serve scattered with basil leaves.