From the Super Mario Wiki
In this minigame, there are three Roulette Blocks that cycle through multiple icons, including a coin, heart, boot, hammer, Mushroom, and a question mark. Mario must hit the blocks to stop the cycles. Each block grants the player a single prize based on the displayed icon. However, if the player manages to match three of the same icon, the degree of reward is multiplied (e.g. five Battle Cards are rewarded instead of one if three boots, hammers or Mushrooms are matched).
"Hit the spinning blocks to stop them. Match three of the same icon to get a fancy prize."