I had a recipe for this that had a homemade sauce, but I was missing a few ingredients. I made do with what I had and it turned out to be very easy and delicious.
Pepperoni - Stuffed Chicken
4 chicken breasts
1 pkg pepperoni
freshly grated parmesan cheese
Ragu Traditional Spaghetti Sauce (or your favorite)
Place each chicken breast between sheets of waxed paper and pound with a kitchen mallet until flattened to about 1/4 inch thickness. (This makes it easier to roll and it also tenderizes it).
Top with pepperoni and cheese. Beginning with smaller end, roll up and secure with toothpicks.
Place in a greased baking dish and cover each chicken breast with sauce. Bake at 350 for about 45 minutes. Sprinkle with parmesan cheese.
Flatten chicken breasts with a mallet to about this thickness: Top with desired amount of pepperoni and cheese. Black olives would also be good.