If you make a post with a dice roll in it, then edit the post, the dice roll will remain the same.
If you make a post with multiple dice rolls, then attempt to "erase" the ones you don't want, your attempts will be invalid (because the sequence of rolls will be remembered, so the 1st/2nd/3rd Rolls will always be the 1st/2nd/3rd Rolls that appear on the page, regardless of how you re-organize them.
If you attempt to modify the range of numbers (IE: typing "roll=10-10" instead of "roll=1-10"), the modification is revealed in the bottom right corner of the dice, so it's clear that you cheated.
The issues with the dice system are as follows:
You can make a roll, delete the post, then roll again for a different result.
And apparently there's another method of getting desired results that Encore demonstrated before, but I don't really know that method.