A step by step video guide to installing RISC OS on an SD or micro-SD card (which must be at least 2GB in size) for use on a Raspberry Pi, using a Windows PC.
The download links referred to in the video are:
Win32 Disk Imager: https://sourceforge.net/projects/win32diskimager/
RISC OS: https://www.riscosopen.org/content/downloads
Apologies for the sound glitch at about 9:20 - I edited this with the speakers off because I wasn't adding any sound, so I didn't know about that until after uploading.