Can you set aside a Golden Mask die to use in the future?
example: Somebody in another room needs a Gold Mask because they have some locked Black Mask dice. Can you set aside a Gold Mask die that you have rolled and roll your remaining dice to get to that room, then use the set aside Gold Mask to release their Black Mask dice?
Somewhat related: If you roll a Black Mask and a Golden Mask on the same roll can you use the Gold Mask immediately to release the Black Mask die or set aside the Gold Mask die to use when their are 2 Black Mask dice?
You can (and should!) set aside dice for later use. It is often wise to keep a golden mask for later use. But of course it might sometimes be faster and more efficient to roll all of your dice, so it depends on how risk aversive you are.
The effect of a golden mask cannot be split between two players (i.e one golden mask cannot heal 1 black die of two different players).