Place the chunks of sweet potato, red and yellow bell peppers, carrots and garlic cloves (skin on) on a large baking tray. Drizzle on the olive oil and sprinkle on the salt, pepper, cumin and paprika. Toss it all together using your hands, then place in the oven for 20 minutes, turning everything over after 10 minutes.
After the 20 minutes, add the red onion wedges and toss everything together again so the onion also gets coated in oil. Put back into the oven for a further 10-12 minutes until the vegetables are tender and slightly charred at the edges. Take out of the oven.
Put quarter of a cupful of the vegetables to one side and place the rest in a large saucepan. Squeeze the garlic out of their skins into the pan too. Pour in the stock. Bring to the boil and simmer for five minutes. Turn off the heat and then blend with a hand blender.
Stir in the parmesan, season to taste and top with the reserved roasted vegetables. Serve with extra parmesan.