romupdatesplit splits the "AmigaOS ROM Update", not the kickstart ROM. Generic KS ROM splitter is pretty much impossible to code.
It's trivial to list the resident tags inside the KS ROM however: Just scan for the resident tag structure (the ID + backref) and then dump the rt_IdString (remember that the ROM pointers need to be converted to buffer pointers: addr - 0xf80000 + bufstart). exec/resident.h has the struct Resident, the ID constant etc.
