Preheat oven to 450 degrees. Cover a baking sheet with parchment paper. Toss the cauliflower with 1 tablespoon coconut oil until coated and spread cauliflower in a single layer on the baking sheet. Bake for 25-30 minutes or until browned.
Meanwhile, in a large pot, add 1 tablespoon coconut oil, onion and garlic. Cook over medium heat until onions are translucent and soft. Add the vegetable broth, water, coconut milk, water, red curry paste, salt, pepper, nutmeg and curry. Heat over medium heat for 15-20 minutes.
Add the roasted cauliflower to the broth.
In a small bowl, combine the arrowroot (or cornstarch) and 1 tablespoon cold water. Stir to combine. Add to the soup and stir. Cook for 5 minutes over medium heat.
Remove the soup from heat and carefully add mixture to a blender (most likely you will need to do this in batches. Blend on low until the soup is smooth but still a little chunky. Return the soup back to the pot. Serves 8-10. This soup is creamier and even better tasting the next day!