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

You may know more than your electrician about audiophile needs- I’ve found this to be the case in the past. The electrician will (or should) comply with Code (as written in the local jurisdiction), but you can and should take a look at some of the threads where @jea48 has discussed best practices. Code is, in a sense, a minimum, and aimed at safety, not sound.
I just went through a new install in a ’new to me’ house. I used a commercial electrical contractor, who seemed to ’get’ some of the stuff better than an ordinary residential electrician (nothing against ordinary residential electricians).
The National Code (assuming you are in the States) keeps getting updated. Since the last time I went through this (having an electrical subsystem installed for a dedicated room), Code now requires arc-fault breakers, wiring the panel to permit them (something I can’t speak to but others might), and I believe childproof receptacles (which, as far as I know, aren’t to a high standard --maybe there is a hospital grade one, but your electrician might give you a pass on your existing outlets). It also depends on whether the work is permitted and requires inspection. (Mine did, it was a large amount of work, involved a big isolation transformer, etc).
If you like your outlets keep your outlets. FWIW, there are unplated Hubbell hospital grade, like the ones Albert Porter sells.