Peel as many carrots as you want to cook and cut them lengthwise and then in half -so you have little shelves of carrots. Don't leave them round or cut on the bias, in other words, because you want a lot of surface area for the sugars to caramelize.
Throw onto a baking sheet, drizzle with olive oil, salt, pepper and put them in a 425 degree oven for 20-25 minutes. Mine got really crispy on the bottom but I liked it that way: if you prefer a more even roast, you can turn them halfway through.
When they are done, spritz with lemon before serving.