Hang on a sec... Wouldn't going that route would mean the post would definitely get edited because I won't always have the same spells prepared on different days?
Unless of course adding a dice roll via an edit is possible... I'll test it on this post.
Edit: Adding dice roll below.
And now changing the above roll. First roll was 1d6 to get 2, this next one is 1d8 to get whatever.
Got 8 on the d8 dice roll.
And editing post again. And editing out the dice roll entirely.
Well, I've shown it's fairly trivial to edit out or change certain dice rolls. Obviously the more dice rolled the less likely it is to inconspicuously change things, so perhaps a standard 3d6 roll or something?