Created ImageMagick tracking bugs for this issue:
Affects: fedora-all [bug 1378790]
Our RHEL ImageMagick packages don't have support for the RGF format. It was only introduced in later upstream versions.
This issue did not affect the versions of ImageMagick as shipped with Red Hat Enterprise Linux 5, 6, and 7, as they did not include support for the RGF format.