Preheat the oven to 400°F. Line a large rimmed baking sheet with foil.
Trim rounded tops off the rolls. Cut each roll in half crosswise. Place the rolls on the prepared pan, cut sides up.
Slice the mozzarella into 8 slices. Use a small ghost cookie cutter to cut each cheese slice. Reserve the trimmings for another use. Cut the olive into tiny bits for the ghost eye
Spread 1 Tbs. pizza sauce on each roll half. Top with a mozzarella ghost. Press the olive bits into each ghost to form eyes.
Bake until the sauce is hot and the cheese just starts to melt, about 7 minutes. Serve warm.