Mix chicken, celery, mayonnaise, 1/2 teaspoon salt, pepper, and pecans.
Taste for salt and add more if needed.
Slice tops off rolls and pull out soft centers—hollows should be large enough to hold about 1/2 cup chicken mixture. (Save centers for bread crumbs.)
Fill rolls with chicken mixture, top with pineapple, and sprinkle with cheese.
Broil 3-4" from heat 2-3 minutes until cheese melts.