Preheat the oven to 180°°C.
Cut the onion, beetroot and tomatoes in half and put them in a baking tin (don’t peel them). Cut the carrot into chunks and tuck between the vegetables together with the garlic cloves unpeeled). Drizzle with the oil, then season with salt and pepper. Scatter the mixed herbs and chilli flakes on top. Toss well.
Bake for about 25-30 minutes, turning the veggies a couple of times.
When the vegetables are tender, let them cool in the tin.
When cooled, remove & discard the skins & stems of all vegetables. Put the flesh into a pan, together with any cooking jus. Add the vegetable stock and bring to a simmer.
Using a stick blender, whiz the mixture into a smooth sauce. Add the parsley and blend a bit more. Add more stock if the sauce is too thick. Reheat if necessary. (Or refrigerate it for later use)
Cook the pasta according to the packet’s instructions. Add the green vegetables to the cooking water for the last 2-3 minutes of cooking. Drain, then keep warm under a lid.
Combine the sauce with the pasta & greens, then serve immediately.