You’ll find README.ROMs in /usr/share/doc/vice/
As the package description says:
”This package does not contain the various ROM images needed to
actually use the emulators; they are available separately from other
locations (see the README.ROMs file). A corporation in the
Netherlands called Tulip holds the copyrights to the ROM images, and
redistribution is not permitted, but VICE itself is unencumbered.”
You’ll find README.ROMs in /usr/share/doc/vice/.
While it’s true that x64 won’t work out of the box, the instructions for making it work are provided. For making it work out of the box there’s probably very little that can be done in Ubuntu. I’m therefore going to mark this bug invalid.