i'm not sure how'd you eff up dice rolls. you could have biased dice that lowers the entropy some. i don't the exact maths, but one six sided dice roll is ~2 bits of entropy. if the dice is bias to a degree, then that goes down a bit. it would lower your overall entropy some, but if you go in excess of the 100 rolls recommended, you'd still have plenty of entropy.
does that make sense? or am i misunderstanding?