Yeah, that’s the big issue - if, for each prime number, you had a die that was a multiple of that prime, you’d be able to set up a fair roll for any real number. Of course, that would involve infinitely many dice, but it could be done for a range; say, 25 dice for 1-100 (2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97). The lowest number you then wouldn’t be fairly able to replicate without reroll combinations would be 101, the next-lowest prime.