After you roll a d20, there are some effects that can modify the result before the calculation is made. Is this a complete list?
- If you don't like the roll (before you know success or failure), throw it away and roll it again
- If you don't like the roll (after you know the result), throw it away and roll it again
- Roll it again and take the better result (oath of enmity)
- Roll it again and take the worse result (various curses)
- replace a die roll with one you rolled before (dice of auspicious fortune)
- add a number to the die roll (heroic effort, adept's insight)
And I think these only apply to a damage roll:
- Brutal
- if it's N or below, re-roll until it's N+1 or above
- if it's N or below, throw away the old roll and re-roll once, taking the result no matter what
- if it's N or below, change to N+1
- if it's the maximum value, roll again once and take the sum
- if it's the maximum value, roll again, take the sum, and repeat if it's maximum value (vorpal/explosive)