I had the same problem and with my pi in the network and under\\retropie\configs\amiga\amiberry\conf\
I opened and edited this file:
it has a line:
there goes the exact name of your 1.3 rom in the bios folder.
of course you can also rename your existing rom to name that's already there.
same procedure needs to be done for the 3.1 kickstart I 've just noticed..
for people unsure about the correct roms: https://github.com/midwan/amiberry/wiki/Kickstart-ROMs-(BIOS) there you can find information about the versions needed including a crc check code, to see if you've got the right file.