You might want to look at the
Instructions for patching firmware 4.26.16704 thread in the Kobo Developer's Corner subforum. The libnickel.so.1.0.0.yaml has patches for Cyrillic, Greek and Bulgarian keyboards which you might look at using as the basic for a Romanian keyboard to replace the extended Latin keyboard.
Download the patch file from the link in the first message in that thread, unzip it and take a look through the files.