Preheat the oven to 180°C, fan 160°C, gas 4. Put the courgettes in a roasting dish in a single layer.
In a small jug, whisk together the lemon juice and olive oil, then drizzle over the courgettes. Turn to coat.
Roast in the oven for 30 minutes. Spoon into a warm serving dish and sprinkle with the chopped mint.