More features happened. Right now, Rockbox is too big to build rombox. If you wish to wait a few more days, I should have my patch done that will prevent Tagcache from building if specified, which will open up a lot of room and will allow you to build rombox again.
EDIT:
Alright. The patch is now committed. All you have to do now is comment out a line in the config file of your device, and it will free up enough room when you build it to have a rombox.ucl.
Specifically, change a line in firmware/export/config-recorder.h (in your case):
#define HAVE_TAGCACHE
to
/*#define HAVE_TAGCACHE*/