Delete me: Software information: RaspberryPi: Beta RPi ROM (RC12) (Rev #1)

The download link provides the beta ROM image (a file ‘riscos’) that is provided in the Release Candidate 12 (RC12) SD card image for the Raspberry Pi computer to run RISC OS.

RC12 itself (download link to Raspberry Pi foundation web site) contains all the elements required to run RISC OS, including the firmware to initialise the Raspberry Pi as well as the HardDisc4 boot files, in an SD card image which can be written to a blank SD card.

Once written to the SD card all you have to do is turn on the Raspberry Pi and it will start up in RISC OS with a lot of preloaded software. The rom image is held inside $.!Boot.Loader where you will see the other firmware files as well:

Directory of SDFS::RISCOSpi.$.!Boot.Loader
.BOOTCODE/BIN     DOS       15:29:38 09-Jul-2013
.CONFIG/TXT       Text      00:00:00 01-Jan-1980
.FIXUP/DAT        DOS       15:29:38 09-Jul-2013
.LICENCE/BROADCOM DOS       12:15:42 27-Sep-2012
.RISCOS/IMG       DOS       10:48:26 13-Feb-2014
.START/ELF        DOS       15:29:38 09-Jul-2013
to be updated

You can see that the RISC OS rom image gets written to (hence updating the datestamp of the file) each time you shut down [this makes sure any ‘cmos’ settings are kept up to date] – the rom image is RISC OS 5.21 (xx-Feb-2014).

These files appear to the Raspberry Pi as the only files in the FAT partition on the SD card as it starts up.

Within RISC OS you will see a complete hard disc of files which means that you can start right away:

When it first starts up you will be shown the Welcome Guide which explains how to configure the machine to enable networking. It also explains how to download more RISC OS software using either the !Store or the !PackMan utility. Each of these shows you a list of RISC OS software, with a detailed explanation of what each bit of software does and lets you choose which items to download.

There are other sites that explain about RISC OS as well – here’s some suggestions:
HowTo shows a RISC OS desktop and lets you click on various icons to see what they do.
If you are new to RISC OS you should first read Introduction to RISC OS – there’s lots of useful stuff to read.