Preheat the oven to 190°C and spray a baking tray with low-calorie cooking spray.
Add the butternut squash, carrot, parsnip and garlic to the tray. Spray the top of the vegetables with low-calorie cooking spray and toss to coat. Pop the tray into the oven for 15 minutes.
After 15 minutes add the aubergine, red onion, beetroot, cherry tomatoes, rosemary and thyme to the tray. Toss the vegetables and pop the tray back into the oven for 35 minutes.
The vegetables should be softened and just starting to turn brown round the edges. Remove the garlic bulbs from the tray and squeeze the garlic from the skins into a food processor with the yoghurt, lemon zest and lemon juice. Blitz until smooth.
Remove any woody stalks from the herbs and drizzle the yoghurt over the vegetables and serve.