As an ex-cop with a no-nonsense, black-and-white world view that has carried over into his new life as a ghoul, he has come to terms with his ghoulhood and yet demands that humans treat ghouls with respect. He has no patience for bigots. Bessie Lynn is his ghoulfriend.
If the Wanderer completes the Tenpenny Tower quest before doing The Power of the Atom, and chooses to destroy Megaton in the latter, Roy will have a short discussion with Burke on Tenpenny's balcony. After expressing shock at Burke's ability to infiltrate the tower, he warms up considerably when he learns of Burke's plan to blow up "that smoothskin shithole".
Upon letting the feral ghouls into the Tower, it is possible that Roy will be killed by security personnel.
It is odd that Roy Phillips has good karma despite the fact that he murders everyone within Tenpenny Tower (including Herbert Daring Dashwood who agreed that Ghouls should be within the tower) and is okay with and happy to nuke and murder everyone in Megaton.
"I already got a plan. They think I'm a monster. I'll show them the real monsters! We'll unleash our feral brethren on them; all those bigoted sons-of-bitches will get torn apart. Trouble is getting past the damn subway access door! You see, there's some kind of escape door that leads from the Tenpenny basement to the subway tunnels. There must be some way to get that open."
"Not sure where you come from kid, but out here in the Wasteland, everything's up for grabs. And you only get to keep what you can hold onto. Tenpenny didn't build that tower. He found it. And took it from whoever used to own it. Now we're gonna take it from him. We tried playing nice, but they shot at us. Fuck 'em. It's time for them and their bigot ways to die."
"Uh-huh? Fine, whatever. Being a Ghoul ain't anything worse than any other thing somebody's got to deal with. Like your stupidity, for example. You can't help it. You were born stupid, or dropped on your head as a kid. Either way it ain't nothing you can change. So you deal with it."