Preheat the oven to 200°C.
Wash the beetroot and trim off any stalks. Then cut them into quarters.
Peel the carrots, cut them in half lengthways then cut each long piece in half.
Peel the onion and cut into quarters.
Peel the garlic and leave the cloves whole.
Stir well and tip the contents on to an oven tray. Roast for an around hour or until the veg is soft.
When the veg is cooked, remove from the oven and allow to cool slightly. When it is cool enough to handle peel the beetroot.
Put all the veg (and any liquid from the tray) into a big bowl and add half the stock. Blitz in a food processor or using a stick blender. Keep adding more of the stock until it reaches a soup consistency (you can make it as smooth as you like). If it's still a little thick then add some more water.
Pour into a pan and heat through gently. Check the seasoning, and add some salt and pepper if necessary.
Serve topped with a drizzle of fat free yoghurt and some rocket. You could even add some crumbled feta.