In a way, I created this problem for myself by being ignorant.

I have NRAAS master controller and woohooer installed (though I am seeing no benefit from the latter), with NRAAS story progression enabled and EA story progression disabled. I don't think I have any other mods that are relevant to the issue.

My sim who I will call Zdenek because that's what I call him, lived in a little house in Roating Heights with his alien baby. He had a romantic interest in Sharpo Marks, who is cute as a button. Their relationship bars were completely filled, they had had a relationship for like 14 days, and I wanted to move Sharpo in. But the only relevant option under any meny was "Friendly...ask to be roommate." The last time I had moved anybody in with anybody was before I had University installed and I had neglected to do all my homework so I didn't know what a terrible option that was, so I did it.

After a couple of Sim days I figured out why Sharpo had not become selectable so I used NRAAS to make him so. That's when the roommates debacle really started.

A female sim showed up unannounced and hung around for days. I thought she was just an interloper so I deleted her in-game and locked the door to all but the household. She came back after a while.I deleted her again and then a different female sim showed up and I deleted her. And then another. By this time I had figured out she was a roommate and dismissed her. A different female sim showed up. I dismissed her too. Each time they ran off like they had an errand they were late for.

I did some more research and discovered I could disable roommates on the phone, so I did.

Okay so now I no longer have extra sims hanging around hogging the computer and sleeping on the couch but two female sims show up on the loading screen and in the scrapbook and relationship panels. I do not think they are the same as any of the ones that I deleted or dismissed, but I am not sure.

How do I get rid of these extra sims for good? They are never physically on the lot so I can't make them selectable and have them move themselves out.

If you really want to get rid of them for good use the MC Total Annihilation feature. That will wipe all traces of them from your game.
If you just want to remove them from the Relationship Panel you can do that by holding down either the Shift or Ctrl Key (sorry not in game, can't remember which) and clicking on the sim to be removed

I can't click on the sim, unfortunately, because they are never physically present on the lot. Or do you mean clicking on the sim portrait in the relation ship panel? (I'll test to see if that is what you meant next time I'm in game)

...and what is the MC Total Annihilation feature, if I did decide to use it, and where do I access it?

thank you! I'll see if I understood the first one correctly, and if it doesn't work, maybe I'll try the second.

Well, I didn't understand the first, because there's no option on the relationship panel portrait except "texting," and "texting" doesn't. apparently, include "kick the roommates out."

I still have not seen the roommates in person. They're on the loading screen, the scrapbook, and anywhere else the household is pictured. When I go into NRaas, the places where the household members are listed sometimes list both of them anbd sometimes list only the first to arrive. And Nraas has no option to move them out.

I don't understgand why!

I went so far as to call up "Total Annihilation" but I chickened out, because I don't know anything about it. In Sims 2, deleting a character is a very bad thing. Is it actually okay in Sims 3?

Yes, in Sims 3, characters can be deleted, and Nraas MC's total annihilation completely removes it/them from game (there is no trace of it/them left, it/they are gone forever).

I may yet do that, depending on how annoying this gets to be. As far as I can tell, the roommates are not actually there, though they appear on the loading screen and in the scrapbook. I was going to try moving my family out and went so far as to make them a new house and gift them the money to move in but then I decided I liked the house they are in better. So I'm doing nothing at the moment.