Preheat the oven to 400°F (200°C) and line a baking sheet with parchment paper.
Toss the cauliflower florets with olive oil, salt, and pepper. Roast for 25-30 minutes until golden and tender.
Heat 2 tablespoons of olive oil in a large pot over medium heat. Sauté the onion until translucent.
Add minced garlic and cumin, and cook for another minute.
Add the roasted cauliflower and vegetable broth. Bring to a boil, then reduce heat and simmer for 10 minutes.
Blend the soup using an immersion blender or transfer to a blender in batches until smooth.
Stir in lemon juice and adjust seasoning with salt and pepper as needed.
Ladle into bowls and garnish with chopped parsley before serving.
