Preheat oven to 425 degrees. Position oven rack to center position. Spray a large baking sheet with non-stick spray and set aside.
In a shallow bowl, stir together the panko bread crumbs, ⅓ cup of parmesan cheese, oregano and ½ teaspoon of the salt and ½ teaspoon of the pepper. Set aside.
Cut each chicken breast into half lengthwise. (10 cutlets) Using a kitchen mallet, pound each cutlet into an even thickness. Salt and pepper both sides of the chicken.
Place a slice of mozzarella near the center of each chicken cutlet. Starting with the small end of the chicken, wrap the chicken over the cheese into a roll. Secure with toothpicks. Repeat until all are rolled.
Brush all sides of the chicken rolls with melted butter. Place the roll in the bread crumb mixture. Use your hands to coat all sides. Transfer each coated chicken piece onto the prepared baking sheet.
Bake for 25 minutes uncovered, or until the juices of the chicken are clear.
Remove from oven and top evenly with marinara, reserving some sauce for serving. Top with more mozzarella cheese. Return to the oven for 5 minutes uncovered until the cheese is melted and golden.
Serve hot with additional parmesan cheese and marinara sauce.