When reading, P0 is an input, thus the device driving the port is an output. The need for pull-ups are related to the output driving the signal, not the input. I do not know of ROMs with open collector outputs, but such animals may exist.

1) check data sheet for your ROM, if it is not open collector/drain, then pullups are not required.
2) verify that your ROM is programmed (write one with 0aah throughout for easy scoping).
3) verify CE and OE polarity, width and timing

This should get you going

Erik