- Ignore the upper 8 bits of PC, which will make the same ROM appear at every 256 bytes.
- Decode the upper 8 bits of PC and only enable your ROM when the correct value (e.g. zero) is matched. If you have any other memories or memory mapped devices connected to the address bus, I presume you'll already have a MUX that could be used for this purpose.
Option 1 is generally fine as long as nothing else shares the address space.