Before each roll you receive an encrypted SHA1 string that contains a Secret Key-RolledNumber-JackpotType, that means the roll number is already predefined before you even click roll dice so there is no way for anyone to cheat.
After each bet ended you can verify its integrity as the server will show you the string unencrypted so if you run a SHA1 on it you will see it was the exact string it was given at the beginning.
In theory, you can just always return "jackpot 0" and never let anyone win a jackpot. Also in theory, if a player has a specific play pattern (for example: under 2x), you could generate outcomes that make the player lose (and obviously in theory, if you would do that, a player could abuse that as well.)
Anyway, basically for a real provably fair mechanism, you should require input from the player like a clientseed (after the player gets the hashed serverseed already.) The end result and jackpot is then calculated with both seeds.
"Also in theory, if a player has a specific play pattern (for example: under 2x), you could generate outcomes that make the player lose"
( the outcome of the dice is predefined before you go to the next bet or set the new bet amounts, so the system won't be able to know if for example you stop and go all in for the next bet as the roll has been already determined ), the jackpot is purely random as you can see people that dind't played the minimum amount already won some but didn't credited because of it.
I know i already have the algorithm for that, but i said to try something new where you get the input before you click bet so you know nothing influence it. If the beta doesn't end properly we can always switch the a client/server seed and that's it, but as i saw on other website some people still acuse websites of cheating.