Preheat the oven to 180°C (350°F/Gas 4). Roast the capsicums, tomatoes and garlic bulb for 10 minutes then remove the tomatoes and set aside to cool. Continue roasting the capsicums and garlic for 30–35 minutes, or until the skin of the capsicums blacken and blister. Cover the capsicums in plastic wrap and allow the capsicums and garlic to cool. When cool, peel the capsicums and tomatoes and put in a bowl, discarding any stalks, skins and seeds. Cut the end off the garlic bulb and squeeze the roasted garlic over the capsicums and tomatoes.
Heat the olive oil in a heavy-based frying pan over medium heat and fry the bread for about 3 minutes each side, or until golden. Drain on paper towel and set aside to cool. Grind the nuts and bread in a food processor to the consistency of coarse breadcrumbs. Add the paprika, red wine vinegar and sofrito and season to taste. Add the capsicums, tomatoes and garlic to the food processor and pulse several times until all the ingredients are well blended, but still coarse in texture. Salsa romesco will keep in the refrigerator for 2–3 days.