Preheat oven to 350 degrees F. Line a baking sheet with foil and lightly spray with non-stick cooking spray.
While the oven is preheating, place the chicken breasts on a large cutting board. If the chicken appears to be a little thicker than thin, pound it down using a meat mallet to about 1/4 - 1/2-inch thick. Season with salt, pepper, and garlic powder or garlic salt, to your taste. Add Italian seasoning, to your taste.
Place a small amount of the cheese over the chicken breasts.
Place about 3 slices of pepperoni over the cheese.
Carefully roll the chicken, from smallest end to largest end as tightly as you can, and secure with toothpicks with the "seam side" facing down. Add more seasonings to your liking.
Place about 2 to 4 tablespoons of marinara sauce on the cooking sheet and carefully transfer the chicken to the baking sheet. You can add an extra pepperoni on top of each chicken breast simply by placing it over the toothpicks and down onto the chicken.
Bake for about 30-35 minutes or until chicken is done. Add marinara sauce over the chicken and sprinkle with additional cheese. Place back in the oven for about 5 minutes, or until cheese has melted.
Remove the chicken and transfer to plates. Carefully remove the toothpicks and serve. You can either cut it into small spiral rolls or eat it just like it is.