Normally, rolls are performed by rolling 2d6 (two six-sided die).
Actions always require a roll to determine the outcome of the action. You roll a Stat when you roll a 2d6 and then apply the modifier of your stat to your roll. The final number determines the outcome of the action.
Battling also requires lots of rolling.
For a more exciting experience that allows for critical fails, you can choose to Homebrew your game and roll 1d12 instead.