I haven't used it, but the description says that it makes a game event occur.

You know how sometimes you get a package delivered to your door, or you get e-mail saying that you've overpaid or underpaid your taxes, or you win a prize for eating a lot of hot dogs, or there's a power failure and all your food spoils? (There are lots more than that, but that gives you a sense of the kind of thing I'm talking about.) I'm pretty sure that those things are game events. So buying a roll of the dice means that some game event will occur -- it could be positive or negative.