No Karma Loss pattern involves a series of speech challanges to get certain residents to move out.
Seeing as Roy is the same as Tenpenny ethically, I tend to avoid this quest line altogether.
Even if you do that Roy ends up killing all the humans in the tower. Which is pretty [censored] up considering they let his stank ass in. But you can then turn around and kill him for no karma loss. But by this point it's useless as Tenpenny Tower has been reduced to a Motel 6. I really, REALLY, do not like this quest. If convincing the residents to let the ghouls move in still ultimately results in their deaths, you might as well just let the ghouls take over and save yourself the hassle. You loose two shop keepers for letting the ghouls move in anyway. It's stupid really. If you flat out kill Roy you lose Karma. Why? The [censored] is planning on massacring everybody in the damn tower. How is killing him bad?
I've tried to do this quest various ways, and all the results svck balls. At least if you want the ghoul mask and the humans to live. So you really only have two choices when it comes to completing the quest. Let the ghouls take over, or kill Roy. If you want to kill Roy without losing karma you can get him to attack you through dialogue, or you can drag a feral ghoul to him and kill him as he attacks you with the feral. Make sure he attacks you first.
Either way, this is the only quest in the game I hate. Especially after blowing up megaton, setting the ghouls up to move in the tower, killing Roy and company right after I get the reward but before they even sets foot in the tower, and all the humans still magically die (on a positive note, it's awesome to watch). Now I have an empty tower, utterly useless. Yet ghouls still spawn sometimes as a "Tenpenny resident" and when you talk to them they say things about how Roy saved them from the wastes or how great Roy's tower is. Roy is [censored]in dead, he did not save you nor does he have a tower. And that's about the time their heads explode.
But after going through all that, and being completely and utterly disappointed. I've decided to never do that P.O.S quest again. Not worth the time, the mask ain't worth the trouble since ghouls ain't hard to kill and I don't wanna look like Freddy that damn bad. [censored] it.