Hi Jurosem, and welcome to the EAB
The answer is simple: The rom you need contains part of AmigaOs, and as such WinUae won't work without it. If you have an Amiga, you can copy the rom from your Amiga to disk, and use it for WinUae. If you don't have an Amiga, then I'm afraid you'll have to buy the rom
Anymore questions? Jusk ask!