Electrical - Romex Wiring and Other Recommended Enhancements

Hello 
you will need to know the  Amps that your system will consume and need to operate correctly and you have to follow local electrical  code .
Based on the amps that you system needs you will pick the correct wire size. Refer to Electrical codes for wire size and grounding. 
Romex is one kind of cable it comes with diffferent amount of conductors and size of conductors.  it is usually embedded in the walls. So if your electrician is pulling a new line he needs to use the right kind of line from panel to the location you need. If inside walls romex is fine if it is external that conduit. 

Best
Technick

And by the way use medical grade outlets 

@thankful, much has been written in various threads that answer your specific questions.
Here is an example that I found:
https://forum.audiogon.com/discussions/romex-and-breaker-switches

Depending upon the length of AC wiring you need to run, and the demands of your audio components I would suggest either 12/2 or 10/2 gauge wire, individual runs to each 20 amp breaker you run and ground according to your local Electrical code.
I’m not sure why the above post suggests medical grade outlets, I would not go in that direction because of the negative effect of various platings used that diminish and cause harshness with the sound. The FIRST Cruze Maestro Outlets are fine as long as you prefer their sound.

Medical grade outlets grip the plugs so much better and their consrtuction is superior to regular outlets

I use cryo’d Pass and Seymour MRI grade outlets - they grip like a vice...
https://www.takefiveaudio.com/products/938-pass-and-seymour-8300-wmri-outlet-cryo-treated/

Make sure the elctrician uses seperate runs of 12/2 and NOT 12/3 - the 12/3 introduces significantly more noise into the wiring.

Hope that helps - Steve