Someone else tipped me off (I think it was Aaron Truitt, but I can't quite remember) that mame4all had a full romset floating around on the net and since the retropie has mame4all among it's emu cores, I decided to give that download. Yeah, I said I didn't want ALL the available roms for MAME, but now that I think of it, it's probably easier to just get the whole set instead of trying to come up with a list of games I want then continue to add more every single time I want to try a new game.
I was actually under the impression that a full romset for MAME would be much more difficult to find and manage than that of any console, but it turns out that the set isn't as big as I thought it would be. I'll see how it goes when I'm finished loading it to the pi.
Now, that 106 romset should be very handy, too. I downloaded it as well and will probably unzip it for use on my PC. Thanks for making that available.