Preheat the oven to 180°C.
Cut the beetroots, onions, red pepper and carrot in half, arrange them in a large baking tray.(Don’t peel them). Add the unpeeled garlic cloves too.
Scatter the dried herbs on top of the vegetables, then drizzle some olive oil and a dash of balsamic vinegar on top. Season to taste, then toss well.
Bake in the oven for 30 minutes or so.
Meanwhile, cook the meatballs according to the packet instruction.
When the veggies are tender, remove the tray from the oven and let them cool a bit. Remove & discard the skin of the garlic, onion, beetroot and red pepper.
Put all veggies in a food processor, including any cooking jus, add the fresh herbs and process until you get a thick smooth sauce.
Pour the sauce into a saucepan, add the passata and stock cube or powder and bring to a simmer. (At this point you could add some spinach, green peas or shredded kale if you like). Add more passata and water, if it's too thick.
Simmer for a couple of minutes and serve with the meatballs.