Preheat the oven to gas 7, 220°C, fan 200°C. Remove the leaves and stalks from the beetroot and peel the skins. Chop into chunks and place in a bowl. Toss with 1 tbsp oil, then transfer to a roasting tin. Cover with foil and cook for 45 minutes. Remove the foil and cook for a further 10 minutes.
Meanwhile, combine the remaining oil, the lemon juice and cumin in a bowl to make a dressing. Combine the beetroot, mint, pomegranate seeds, spring onions, and toss with the dressing to serve.