The RISCOSbits FAST machine currently needs a custom ROM - you cannot download the generic build from ROOL and use that.
So RISCOSbits have been releasing regular ROM updates which add new features, fix bugs and align the code base. The latest release essentially updates the ROM to match the current RISC OS version and does not add any new features (or bugs!).
The update is available on a special area (RISCOSbits tells you in the FAST manual) and contains a new ROM image which you just need to replace the current version on your SD card with the new one. Being picky, it would be nice to have a little utility to do this, but it is not difficult.
You can access the Open Loader directly for the Configuration via !Boot. You can also access the SD card via the !SDCtrl app in Apps or modify the SD card on another machine. The SD card is accessible from the front panel (so you do not need to open the case) but it is quite subtle if you are not looking for it. If you have any problems, you will find Andy super-reactive and helpful.
Having installed it, you will find your system bang up to date. Hopefully it will be 5.30 next time!
As an aside I have been using my FAST machine as my main RISC OS system since 2023 and now rarely boot anything. It is FAST and very slick....