Adding Roll Tag BBCode?

[DL_Ashe]

Hi there,

I'm trying to add/create a custom BBCode that will allow members of my forum to call the [roll] tag to roll dice for RPG play-by-post games.
Something along the lines of: [roll=Dice]Action Description[/roll].

So in a post it outputs something like:
DL_Ashe swings a cat around: 6d8 (12,13,16 = 41) + 4 = 45

I'm looking to make this handle any kind of RPG dice, and allow for multiple dice to be thrown in a post.

Is that easily achievable? Ideas?