The Internet Archive hosts several community-curated collections of Amiga firmware, ranging from the earliest versions to later professional releases:
Amiga Kickstart ROMs on Archive.org: A Guide to Preservation and Emulation amiga kickstart roms archive.org
Includes the ubiquitous v1.3 (essential for most A500 games) and v3.1 (used for later AGA-compatible machines like the A1200). amiga kickstart roms archive.org