Luigison has demonstrated a trigger used in #tmk: !d! Type "!d (insert number here)" and Mushroom_Boy will roll a die woth that number of sides (or flip a coin if you put in 2 as the number). He'll roll you if you type !d0 or !d1, though.
To use this, you must enter #tmk and either get voiced or get someone with +v or above to do it for you.