Heat your oven to 200°C/Fan 180°C/Gas 6. Peel and chop the sweet potatoes into 1 cm pieces. Place on a baking tray. Drizzle with 1 tbsp olive oil and season. Toss to coat the potatoes in the oil. Slide into the oven. Set the timer for 25 mins.
While the potatoes roast, roughly chop the tomatoes and place in a roasting tin. Peel and finely chop the onion and add to the tin with the unpeeled garlic cloves and 1 tsp smoked paprika. Drizzle with 1 tbsp olive oil and 1 tbsp red wine vinegar. Season with salt and pepper. Toss to mix. Roast below the potatoes for 25 mins till softened.
Rub the cod fillets all over with 1 tsp olive oil each. Season with salt and pepper. Sprinkle over 1 tsp of the smoked paprika. When the sweet potatoes have cooked for 15 mins, nestle the cod fillets on the tray with them. Roast for a further 10 mins, till it just flakes (this should take you to the 25 mins you set your oven timer for).
Take the cod and potatoes out of the oven. Loosely cover with foil and set aside.
Take the tomatoes out of the oven when they’re ready. Squeeze the garlic cloves from their papery skins. Tip the tomatoes, garlic and onion into a bowl with the tin juices and use a hand-held blender to blitz together. No blender? Squash the garlic cloves, then stir back into the tin for a chunkier sauce.
Stir the sweet potatoes into the tomato sauce. Taste and add salt or pepper if you think it needs it. Roughly chop the parsley leaves and stir half into the potatoes. These are your batatas bravas.
Mix another 1 tbsp red wine vinegar with ½ tbsp olive oil. Pour over the rocket and toss to mix.
Serve the cod with the batatas bravas and a handful of rocket. Garnish with the remaining chopped parsley.