For both flash drives I formatted in Windows and created a “retropie” folder. When I inserted the 2gb stick, RetroPie recognized it and populated the “retropie” folder. I don’t think I did anything else on the RPi to format or mount. When I performed the same process with 128gb stick, RetroPie never populated the “retropie” folder. I even left it plugged in overnight. I did confirm that the disk was being recognized by the RPi. .
I went through the method described in your link and it did work. The only issue is that Windows no longer recognizes the stick, so I have to transfer the ROMs over FTP instead of just plugging it into my PC with the stored ROMs. It’ll take a little longer but I guess I should have to do it once.
Thanks for the tip!