Preheat the oven to 200C/180C fan forced. Line a large baking tray with non-stick baking paper. Place beetroot and carrots in a single layer on the tray. Spray with olive oil and season with pepper. Roast for 40 minutes or until golden and tender.
Meanwhile, place the lentils and water in a large saucepan. Bring to the boil. Reduce heat to low. Simmer for 20 minutes or until just tender. Drain well.
Place the lentils, onion, vinegar and oil in a bowl. Gently stir to combine. Set aside for 5 minutes.
Add the beetroot, carrot, pepitas, mint and parsley to the lentil mixture. Season with pepper. Toss to combine.