Cook the root vegetables - Heat one tablespoon olive oil in a large pot or Dutch oven over medium heat. Add the onions and cook, stirring often, for 4-5 minutes or until the onions soften and turn translucent. Add the carrots, celery, and sweet potatoes and mix well to combine with the onion. Cover and continue to cook over medium heat for 10-15 minutes, stirring often.
Add the cauliflower- After approximately 10 minutes or so, once the vegetables have had a chance to start softening, stir in the garlic and ginger and sautè for approximately 1 minute. Add the cauliflower florets and mix well to combine. Add the fresh sage, salt, pepper, and cinnamon.
Add the broth, roasted acorn squash, and simmer - Add the water or vegetable broth to the pot and bring to a boil. Cover and reduce heat to a simmer. Allow vegetables to simmer for approximately 15 minutes. In the meantime, scoop the soft flesh from the roasted acorn squash and transfer to the pot. Continue to simmer for an additional 15 minutes.
Blend soup - Once all the vegetables have softened, remove from heat and grab a blender, food processor, or immersion blender. Working in batches, fill your blender approximately half full with the acorn squash and broth mixture and blend until completely pureed. Pour your pureed soup into a new pot. Repeat until all the vegetables have been pureed into soup.
Season to taste - Over low heat, stir in the 1/2 cup of half-and-half and season with salt, pepper, and additional cream to taste. Stir often to prevent soup from burning.
Serve - Serve with all your favorite toppings including homemade croutons, pumpkin or sunflower seeds, fresh herbs, shredded cheese, bacon bits, or pomegranate arils, if desired.