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The only thing about the ROM is the Boot ROM Version in the System Profiler. Don't you mean RAM?
 
ROM = Read-Only Memory, like CD or DVD ROMs.
RAM = Random Access Memory, temporary data storage.

Go under the :apple: menu and choose "About This Mac" and you'll see the RAM of your machine next to Memory.
 
Why do you need to know how much ROM it has?

What will you do with this information?

What will happen if you never have this information?

What if the answer is "no ROM"? I mention this because firmware in recent models is in Flash memory, where it can be reprogrammed with Apple-issued firmware updaters.
 
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