One last thing.  I also now understand why you guys generate a new server seed hash for each roll.  As I mentioned in one of my previous posts, cryptographic operations are expensive and you want the front end to be as responsible as possible.  So to accomplish this, you have a pre-generated list of server seeds / hashes on the back end ready to be compared against and on the front end when the user clicks roll all you have to do is look up the seed in a map and send this seed back to the front end for verification.  Like:

hashMap = {"server_seed_hash_1": "seed_hash_1",
"server_seed_hash_2": "seed_hash_2",
"server_seed_hash_3": "seed_hash_3"}

return hashMap["server_seed_hash_1"]

Kind of a smart design to be honest as you've been able to make it performant and responsive.