Preheat oven to 400 F.
Toss celeriac and rutabaga in a bowl with 2 teaspoons of olive oil, salt and pepper. Dump them on a sheet pan and put them in the oven.
Toss the butternut squash in the same bowl with 1 teaspoon of olive oil, salt and pepper. Add them to the pan in the oven after the celeriac and rutabaga have roasted for about 15 minutes. Roast vegetables for 15-20 minutes more, until they are caramelized and fork-tender.
In the meantime, rinse the lentils. Heat 2 cups of water and 2 cups of water in a soup pot over medium heat. Add the lentils, bring to a boil, and then lower the heat to a simmer. Partially cover the pot and cook the lentils for about 15 minutes until soft.
When the lentils are done add the roasted vegetables. Mix the coconut milk with the miso and Harissa and add it to the pot. Add the greens and cook until the greens are slightly wilted.
Blend the soup with an immersion blender. You can do it in the blender, but remember to take the top off of the blender and use a kitchen towel over the opening if you are blending hot soup.