Preheat the oven to 200ºc/Gas 6.
In a large roasting tin, add the oil and place in the oven to heat through for 5mins.
Add the potatoes, paprika and some salt and pepper and toss together in the hot oil. Return to the oven and roast for 30-40mins, turning halfway through until golden and crisp.
Meanwhile, to make the sauce, heat the oil in a saucepan, add the onion and garlic and fry for about 5mins over a medium heat. Stir in the paprika, followed by the tomatoes and tomato paste. Simmer for 5 mins, stirring occasionally until the sauce is reduced and thickened. Season with salt and pepper.
Arrange the potatoes on a plate, spoon over the sauce and serve.