Preheat the oven to 220C/200C Fan/Gas 7. Tip the potatoes, cauliflower, onion, garlic, ginger, turmeric, chilli, spices, oil and salt into a large roasting tin, and mix well. (If everything doesn’t fit comfortably in one layer, transfer half of the mixture into a second roasting tin.)
Transfer the tin/s to the oven to roast for 40 minutes.After 40 minutes, add the cherry tomatoes and boiling water (evenly between the two if you are using two tins), then return to the oven for a further 20 minutes, reducing the heat to 200C/180C Fan/Gas 6.
Taste and adjust the salt as needed, squeeze over the lime juice, and scatter with the fresh coriander before serving with hot rice or naan breads.