Preheat the oven to 375 F. Line 2 sheets with parchment paper.
Toss the sweet potatoes and cauliflower with 1 tbsp avocado oil and cumin. Spread into a single layer on the prepared sheets. Roast until the veggies start to brown at the edges and the sweet potatoes are tender - about 30 minutes.
Heat the remaining avocado oil in a large saucepan over medium heat. Add the onions and saute for 5-7 minutes, until they soften.
Ad the cooked sweet potatoes, cauliflower and onion in a blender or food processor. Add the veggie stock and blend.