I'm a new DM for four people who are all friends (I am also friends with all of them). During the game, I observed one player turn a D20 from a lower number to a higher number a couple times with her thumb when all the players were rolling simultaneously. Both times, she verbally told me she rolled the lower number, but I also think she saw me observe her change the roll. At the time I chose to let it go, with a resolve to watch her more closely in the future.
However, another player approached me a couple days after the game, to tell me that this player was changing her rolls, and that they feel it is unfair that this player is manipulating their rolls. I'm not entirely certain that this second player didn't just observe the times I saw however.
I don't want to accuse someone of cheating if they were not, but I also don't want cheating to continue if it is in fact occurring. What is a good approach to dealing with this situation? Should I talk to the player in question, or make sure only one person rolls the dice at a time, or some other approach?
Additional information that answers questions that have come up in comments:
- We were not using any form of dice tray or dice tower.
- Each player has their own unique colored dice.
- I am not assuming that this player is cheating, however it is possible the second player who brought it up to me could be assuming so.
Best Answer
Use a Rolling Tray
Since another player has already mentioned it, your simple solution is to use "a rolling tray" or something similar. Any roll that does not land on the rolling tray does not count.
What is a rolling tray?
It can be anything. Something about the size of a Monopoly® box, turned upside-down, is big enough to accommodate this simple table top tool. An upside down Frisbee® is another nice option. Players toss their dice into the tray and whatever comes up is seen by all at the table.
While you could use a piece of green felt, the advantage to a tray with edges on it, like an upside down box top, is that it keeps the dice from rolling off the table/out of the tray.
How does this help your situation?
Since it appears that you don't want to confront someone and have the social friction of a cheating accusation arise, the rolling tray has a practical side: dice don't disappear, don't fall off the table, and you thus don't have to re-roll as often. This is the only feature you need to emphasize when introducing a tray as the new normal.
Another advantage is that when using miniatures, a rolling die is less likely to knock one over or out of place.
FWIW, I've run into die manipulators and various cheaters over the years. How one handles that is very much a function of the group's interpersonal dynamics. If your group is mature enough to handle a potentially difficult discussion, Molot has some solid advice here.
If you don't mind spending a few bucks, a dice tower is another option. There are a variety of models. I just linked to that one as an example. Thanks to @LeeMosher for the suggestion of the upside down Frisbee®.