Cloanto has held the license for Amiga ROMs for decades. Their package is the most reliable source. Value: It includes every ROM version from 1.0 to 3.1.
If you are looking for the latest , you can purchase digital or physical copies directly from Hyperion or authorized Amiga retailers like AmigaKit or Amedia Computer. How to Install Kickstart ROMs for Emulation kickstart rom amiga install download
This usually indicates a checksum mismatch or a corrupted ROM file. Try a different version. Cloanto has held the license for Amiga ROMs for decades