Preheat oven to 200°C (390°F). Line a baking sheet with parchment paper and arrange carrots all over in a single layer. Drizzle them with oil, then distribute the oil all over the carrots with your hands. Lastly, sprinkle all with salt and rosemary.
Bake for 30-40 minutes (depending on the thickness of the carrots), until slightly brown and tender (you should be able to easily stick a fork or a knife in them).
Remove from oven, transfer to a serving plate and sprinkle with more herbs.
You can roast other vegetables, like cauliflower or broccoli, the same way.
You’ll notice a few carrots look almost black – they’re not burnt, but the really deep purple carrots only turn darker when baked.