Copying ROMS ?

I have several vintage computers (Epson HX-20). A couple of these have been customized and have had the BASIC ROMS removed and some other ROMS installed. I'd like to go back to the original BASIC machines. I do have one original HX-20 that has the BASIC ROMs. But when I tried to copy the ROMS into my Data I/O Model 22, only FF shows up. I presume these ROMs are protected somehow. However, they function and must function in use, so the data should be recoverable. Anyone have any suggestions on how to make copies of these old BASIC ROMs? Thanks, Mike