Preheat your oven to 350°F if you want to warm the croissants.
In a medium bowl, combine the shredded chicken, chopped romaine lettuce, Caesar dressing, and grated Parmesan cheese. Mix well until everything is evenly coated. Season with salt and pepper to taste.
If desired, slice the croissants in half and place them on a baking sheet. Toast in the oven for about 5 minutes, or until they are warm and slightly crispy.
Remove the croissants from the oven. Spoon the chicken Caesar mixture generously onto the bottom half of each croissant. If using, add a slice of crispy bacon on top.
Place the top half of the croissant over the filling and serve immediately.