Pre-heat oven to 450 F degrees. Chop all your veggies.
Once the oven is hot, toss the cauliflower with 1 tbsp of olive oil, salt and pepper and spread out in a single layer and roast, for 20 minutes total, flipping cauliflower with a metal spatula halfway through.
Heat olive on a heavy bottomed pot or Dutch oven. Add onions and sauté over medium-low heat for about 10 min, stirring occasionally, until tender and barely starting to brown. Stir in celery root, fennel, ginger, and garlic and sauté for 5 minutes, stirring occasionally.
Add cauliflower, veggie stock and salt to pot. Bring to a boil, lower heat, cover, and simmer for 25-30minutes, until veggies are tender. Remove from heat.
Working in batches, puree soup in a blender, until very smooth,
Pour blended soup into a large saucepan and add salt and pepper to taste.
Laddle soup into bowls, sprinkle with any topping your heart desires and enjoy.