Preheat the oven to 390°F (200°C) and position a rack in the center.
Take the 12 peeled carrots and, on a cutting board, cut them on the diagonal into pieces about 2" (5 cm) long. Cut any particularly thick pieces in half so all pieces are roughly the same size.
Strip the leaves from 4 sprigs rosemary into a roasting tin. Add 2 tablespoons olive oil to the tin and stir or swirl to coat the tin and rosemary leaves.
Add the prepared carrots to the roasting tin. Sprinkle 1 teaspoon salt and ½ teaspoon pepper over the carrots. Use your hands or tongs to toss the carrots so they are evenly coated with the oil and rosemary, then spread them out in a single layer.
Roast the carrots in the preheated oven for 30 minutes, or until a knife easily pierces the carrots and they are tender.
Remove the tin from the oven and drizzle 2 tablespoons maple syrup evenly over the carrots. Toss gently to coat, or turn the pieces so the syrup is distributed.
Return the carrots to the oven and roast for 5 more minutes, or until the syrup is sticky and the edges have a slight char.
Remove from the oven and serve immediately.