I don't know about LRF and RTF, but for ePub all that is available are the generic font families serif, sans-serif, and monospace. The fonts are provided by Adobe, and have very little support for the extended unicode character sets. I think the Adobe serif font may also be used when "reflowing" PDFs.
You can embed a font in the ePub, and you can also over ride the default fonts by hacking the firmware. See
Replace DEFAULT epub fonts! (PRS-505).