Preheat the oven to Gas Mark 5, 190°C, fan 170°C. Meanwhile, peel and slice or cube your chosen veg.
Put the veg into an ovenproof dish, about 23cm (9in) square. Add the garlic, oil, season and toss well.
Roast for about 40 minutes, stirring halfway through, until the veg is tender and starting to caramelise in places.
Beat the eggs together with the chopped herbs and salt and pepper. Take the dish out of the oven, pour the egg evenly over the veg and scatter over the grated cheese.
Return to the oven for 10-15 minutes until the egg is all set and the top is starting to colour. If your oven has a grill, you can use that to accelerate the browning of the top. Leave to cool slightly, then slide the frittata out on to a plate or board. Serve warm or cold.
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