- Preheat the oven to 200°C.
- Mix the olive oil, lemon zest, lemon juice, garlic powder and celery salt with the herbs and crushed garlic in a bowl and set aside.
- Put the prepared Purple Majesty potatoes, onions, leeks, peppers, parsnips and carrots in a large, deep roasting tin. Now drizzle all over with the lemon and herb marinade and season with freshly ground black pepper.
- Roast for 25 minutes, stir everything around, then add the cherry tomatoes and stir again so that everything browns evenly.
- Roast for a further 25-30 minutes, or until cooked through and nicely browned on the edges.