I lived in Rome for four years. A good restaurant is best assessed by the number of locals in the room. In Italy you pay for real tablecloths and the visual effects, but not for food quality. My personal favourite is a hole-in-the-wall near Campo Dei Fiori, serving deef fried baccala (salt cod) and simple side dishes. People in Armani and people in overalls rub shoulder-to-shoulder, the wine is cheaper than the water and you eat with yor hands, but the quality...
This obviousy is not a grand romantic occassion, but for August outdoors, it is well nigh unbeatable. For a food assault (no, not romantic) try l'Ambasciata del Abruzzo. The only question they ask is "white or red?". They might as well ask at the end of the meal "cab or hearse, sir?"