In a large mixing bowl, combine the chopped chicken, ranch dressing, Greek yogurt, diced celery, and red onion. Mix thoroughly until all ingredients are well coated.
Season the mixture with salt and pepper to taste, adjusting as needed.
Slice the whole grain rolls in half and lightly toast them if desired for added crunch.
On the bottom half of each roll, layer a generous amount of the chicken mixture.
Top the chicken mixture with shredded lettuce, sliced tomatoes, and shredded cheddar cheese.
Place the top half of the roll on the sandwich and gently press down to compact it slightly.
Slice the sandwiches in half for easier handling, if desired.
Garnish with freshly chopped parsley for added color before serving.
Notes
Serve with pickle spears and extra ranch dressing for dipping.