ROM - COMBINATIONAL MEMORY?
Since you cannot change the contents of a true ROM, it should be clear that the output depends only on the inputs, ie, which memory cell is selected by the address inputs, if the output is enabled, etc.

This would not, however be true for a synchronous ROM with registered inputs or pipelining.

And it is not true for any sort of RAM, PROM with still alterable state, EPROM, EEPROM, etc as in those cases inputs can establish state which will affect the future relationship between inputs and outputs.  However it may be true if certain inputs (write enable, erase enable, or a voltage needed for that) are prohibited.