Preheat the oven to 400°F (200°C). On a baking sheet, toss the cauliflower florets with olive oil, salt, and pepper. Roast in the oven for about 25-30 minutes, or until golden brown and tender.

While the cauliflower is roasting, prepare the roasted garlic. Cut the top of the garlic head off to expose the cloves, drizzle with a little olive oil, wrap in foil, and roast in the oven for about 30 minutes, until soft and caramelized.

In a large pot, heat a tablespoon of olive oil over medium heat. Add the diced onion and sauté for 5-7 minutes, until soft and translucent.

Once the cauliflower is roasted, add it to the pot with the onions. Squeeze the roasted garlic cloves out of their skins and add them to the pot as well.

Pour in the vegetable broth and bring the mixture to a boil. Reduce heat and let it simmer for about 10 minutes.

Using a blender or an immersion blender, blend the soup until smooth and creamy. If the soup is too thick, add a little more broth to reach your desired consistency.

Stir in the shredded cheddar cheese and paprika (if using) until melted and fully combined. Taste and adjust seasoning if necessary.

Serve hot, garnished with fresh parsley if desired.