The 500 requires a Kickstart switcher or an accelerator with ROM emulation (e.g., PiStorm, TF536). The 600 (ECS chipset) can use a physical 3.2 ROM designed for the 600's 4-pin header.
If you want a modern Amiga experience but cannot afford the $30 license, consider these legal alternatives:
Crucial Tip: When you buy the digital version, you are not buying a "file." You are buying a license. The actual ROM file is extracted by running the official AmigaOS Installer script from the downloaded ISO.
There are two primary ways to obtain the ROM files legally.
The Amiga 500 and 600 often use DIP ROMs or have the ROM soldered to the board.