If you have leftover escarole, sauté it in olive oil with garlic as a side, or stir it into soup.
In a small bowl, whisk together lemon juice, garlic, rosemary, salt and pepper. Slowly add oil in a stream, whisking, until emulsified.
Combine escarole, tuna, beans and roasted bell peppers in a serving bowl. Gently toss in lemon vinaigrette until coated. Sprinkle with cheese, if desired, and serve.