Combine the cooked chicken, crumbled bacon, and ranch dressing in a medium-sized bowl and toss well to coat all pieces evenly.
Butter the cut sides of each hoagie roll, which helps keep the buns crisp and adds flavor.
Warm a large skillet over medium heat and toast the buttered sides of the rolls until they turn golden and crispy, about 2 to 3 minutes.
Take the toasted rolls off the skillet and give them a minute to cool slightly to keep the lettuce fresh.
Divide the chicken mixture onto the bottom halves of the rolls, spreading it out generously.
Layer shredded lettuce evenly over the chicken mixture, then add two tomato slices per sandwich followed by some thinly sliced red onion.
Top each sandwich with the roll’s top half and press gently to secure all the ingredients.
Serve the sandwiches immediately while the rolls are still warm and crunchy for the best experience.