Preheat the oven to 400 degrees F.
On a sheet pan, toss the sweet potatoes and cauliflower with 1 tablespoon olive oil, 1/2 teaspoon kosher salt and 1/4 teaspoon black pepper. Spread the vegetables into a single layer.
Roast the sweet potatoes and cauliflower for 25-30 minutes, flipping over halfway through roasting, until they are browned on the edges. Reserve about 1/4 cup sweet potatoes and 1/4 cup cauliflower to garnish the soup.
Heat 1 tablespoon olive oil in a large saucepan over medium high heat. Sauté the onions until they are starting to soften and turn translucent, about 4-5 minutes.
Add the garlic, cumin, curry powder and smoked paprika. Continue sautéing until fragrant about 30 seconds.
Add the roasted potatoes and cauliflower and vegetable broth and simmer for 10 minutes.
Puree the soup in batches by transferring it to a blender. Or puree it in the pot with an immersion blender until smooth.
Warm the soup as needed on the stove over low heat. Divide into bowls and top with reserved roasted sweet potatoes and cauliflower and parsley.