Step 1 Use a fork to flake the halibut into bite-size pieces and place in a large mixing bowl. Add the diced bell pepper, green onions, parsley and celery. Toss to combine.
Step 2 In a small bowl, mix together the mayonnaise, lemon juice, tapenade and pepper flakes. Add salt and pepper to taste. Gently toss the salad with the dressing.
Step 3Split the sandwich rolls in half and toast them. Place a lettuce leaf on the bottom half of each roll. Divide and mound the halibut salad on top. Cover with the top half of the roll, arrange on dinner plates and serve immediately.