H...
Hmmm my understanding is that the precious metal 15300s (RG and YG) are already on straps. If that's the case, then the ROC straps should fit without adjustment.
The plots that are included on the precious metal 15300s are already manufactured to connect to a strap (rubber or leather) The problem arises when you have a SS 15300... which has plots that are integral to the bracelet... i.e. there is no way to separate the plots from the bracelet... and that is attached as one piece to the watch itself.
With the precious metal ones you can freely detach the plots.
Does that help answer the questions?
Zack