Preheat oven to 425F & line a baking sheet with parchment paper.
In a bowl, combine the cauliflower, 2 tablespoons avocado oil & curry powder. Toss to coat, transfer to the prepared sheet pan and spread into a single layer. Roast in the oven until golden brown and tender, around 30 minutes.
Preheat a Dutch oven or stockpot over medium heat for 5 minutes. Add 2 tablespoons avocado oil & heat until shimmering. Add onions and cook until soft and translucent, 4 minutes. Add garlic and cook 1 minute. Add chicken stock, water & yams, raise the heat to high & bring to a boil. Cover with a lid & cook until yams are fork-tender, around 12 minutes.
While the yams cook, preheat 1 tablespoon avocado oil in pan over medium-high heat. Add the sausage and cook until crispy & well-done. Add the white parts of the scallions & the chili pepper. Cook an additional 2 minutes. Set aside.
Working in batches so as not to overfill the blender, transfer the roasted cauliflower & the soup to a blender & blend until smooth.
Return the blended soup to the pot, taste for seasoning & adjust with salt & pepper as desired. Ladle into serving bowls, garnish with sausage crumble & green parts of the scallions & serve.