Preheat the oven to 200C/180C fan. Line a baking tray with foil.
Toss the carrot batons with the olive oil, lemon zest, thyme, cumin, salt and pepper. Spread on the baking tray in a single layer.
Roast for 25-30 minutes until the carrots are tender and caramelised at the edges.
While the carrots roast, put the couscous in a bowl. Pour over the hot vegetable stock, cover with a plate and leave for 10 minutes.
Fluff the couscous with a fork and season. Squeeze the lemon juice over the roasted carrots.
Serve the carrots on top of the couscous, scattered with crumbled feta if using.