By checking that the hash matches the seed after the roll when it is revealed. Most Bitcoin casinos use the same system that we do. it's only a few of the newer ones that use static servers seeds. I'm trying to work out if you are deliberately spreading false information or you are just incredibly thick.
Are you going to switch to constant Server Seed Hash like on Stake.com generation in the future?
There's no reason to. The existing system is completely provably fair and good enough for most other sites. Just because a few sites have done it differently it doesn't mean that everyone elsehas to completely rewrite their code to copy it.