The package file RO_Render provides a mapping between fonts and the RISC OS fonts that should be used to render them. Its primary use is for virtual fonts.
The format of the file is a sequence of lines of the form:
<TEX font name> <RISC OS font name>
For example:
rphvr Homerton.Medium rpcrb Corpus.Bold rpcrr Corpus.Medium rpsyr Symbol rptmr Trinity.Medium