Heat your oven to 200°C/Fan 180°C/Gas 6. Halve the spaghetti squash. Scoop out the seeded middle bit with a spoon. Place on a baking tray. Drizzle with ½ tbsp oil. Roast in the oven for 30 mins till just soft.
Cut the tomatoes into wedges and scatter on a baking tray, along with the olives, a pinch of chilli flakes, 1 tsp dried oregano, 1 tsp oil and some seasoning. Toss together, then bake for 20 mins on the shelf below the squash.
Take the squash out of the oven and set aside to cool. Tip the tomatoes and olives into a food processor. Add the balsamic vinegar and blitz to make a sauce. No food processor? Tip into a bowl and use a potato masher to crush everything together.
Using your hands, peel the skin from the cooled squash. Pull the squash's flesh apart with two forks to create 'spaghetti'. Spread the squash spaghetti back out on the baking tray.
Pour the tomato and olive sauce over the squash spaghetti. Toss together till well coated.
Cover with a layer of greaseproof paper. Put back in the oven for a further 10 mins to warm the spaghetti through.
Serve the spaghetti squash and sauce with handfuls of the rocket.