To roll dice, simply type
[dice=y]x[/dice]
y being the number of dice you would like to roll, x being the number of sides you'd like the dice to have.
EXAMPLE: The 6-sided dice lands on 3
The 6-sided dice lands on 4

If you suspect someone is cheating with the dice, you can simply hit the "quote" button on their post to see what they truly typed. If they have used the dice tool, you will see something like [dice]6[/dice], and if they have cheated, you will see something like The 6-sided lands on 2.