They could make it semi random meaning:
As long as you keep an item in the crafting slot (traits or properties), every trait / property combination you don’t keep and reroll is removed from the possibilities.
This means that you can not roll the same thing again until you rolled every possibility.
In case you messed up and rerolled the thing you actually wanted remove the item from the crafting slot and put it back in cleaning up the history.
This is still a system that works with your beloved RNG but will not **** anybody over.
Note that if you don’t tell anybody that it works this way most people will still believe it’s random and that’s all that counts in the end, satisfied costumers and SIGMAR’s RNG.