You will not find a rom of a CD game. You will find ISO or other CD image formats and these will be 700 MB each. You will need to then burn a copy or use a program like Alchohal 120 or Demon Tools to create a virtual CD-ROM drive and mount the image onto it.

A good PSX emulator is ePSXe.

Emulating this stuff is far more complicated than emulating SNES games and older stuff in general.