The only way to make fair to investors is to pull the random number from a provable RNG such as a hardware one. Services such as random.org offer this. Of course, this translate CP risk from the OP now to a different 3rd party.
I don't see how this works at all.
I could just tell you I'm using random.org, but 1 in 100 times I don't use random.org at all, I just pick a number that makes you lose. How do you tell?
That way it's not provably fair at all. Now both gamblers and investors have to trust that I'm really using random.org and not just picking whatever rolls suit me.
There's a game called "insanity dice" that uses random.org. I think it's intended as a joke.