Preheat oven to 200°C. Mound carrot sticks on a baking tray. Sprinkle with salt and drizzle with oil. Toss gently to coat. Spread out on tray in a single layer.
Roast 10 minutes. Stir in rosemary. Roast until crisp-tender and lightly browned in spots, 7 to 10 minutes.