Heat oven to 375°F. Spray 2 regular-size muffin cups with cooking spray. Place rolls on cutting board; let stand 10 to 15 minutes to thaw.
Make a horizontal slice in side of each roll, cutting almost all the way through and making a pocket, but leaving attached 3/4 of the way around. Spoon 2 teaspoons pizza sauce into pocket in each roll. Place 3 slices pepperoni over sauce in each roll; carefully spoon 1 tablespoon cheese into each. Place in muffin cups; press gently to close.
Bake 9 to 11 minutes or until cheese is melted and bubbly. Remove from muffin cups; serve warm.