Place a chicken breast half between 2 pieces of plastic wrap. Using the flat side of a meat mallet pound chicken lightly into a rectangle about 1/8 inch thick. Remove plastic wrap. Repeat with remaining chicken.
Place a slice of prosciutto and a slice of cheese on each chicken piece. Fold in the bottom and sides; roll up. Secure with wooden toothpicks.
In a medium skillet cook rolls in hot butter over medium-low heat for 20 to 25 minutes or until no longer pink (170 degrees F), turning to brown evenly. Remove toothpicks before serving.