Take a large baking pan and line with parchment paper
Peel your carrots and chop them about 1/2 inch thick. Cutting on a diagonal is best. Put them in a large bowl. Drizzle them with two tablespoons olive oil and the salt stirring them well to coat. Add to the baking sheet so they are all in a single layer.
Put them in the oven for about 15 minutes and toss them. Return to the oven for 10-25 more minutes, when they are easily pierced with a fork and are slightly caramelized at the edges, they are done. Set aside.
In a medium / large pot over medium heat, add 1 tablespoon of olive oil. Add the chopped onion and simmer until translucent. Add the chopped garlic and simmer for another minute until fragrant but not browned.
Add in the vegetable broth or chicken broth and dill and stir well
Add in the roasted carrots and bring to a boil. Turn down to a steady simmer for 15 - 20 minutes.
Add in the butter until it is melted and incorporated.
Remove from the heat. Let it cool for 5-10 minutes.
Transfer the soup to a blender in batches and blend until smooth.
Add salt and pepper to taste.
Add in more broth if the soup is a bit too thick for your liking.
Notes
You can top this soup off with a swirl of thick cream and finely diced chives.-This soup keeps in the freezer for a few months or in then fridge for 3-4 days.