There seems to be two different ideas going on that she needs human warmth to live and that Roxannes life force is making her live.
It's all a bit messy, but I think the idea is that Roxanne's life force is what allows Ang to live at
all, and then she also periodically needs a boost from a living heat source on top of that. One person's life force wouldn't be enough by itself to keep one other person going, as long as it has to keep the donor living minimally too. It would be weak. It's divided between two people.
Claude North VO. Oh, how precious his thick, romantic vocal tones are. I don't know why his character didn't take off as a teen heartthrob, the throaty devil.
Is DS a place with lots of sad deaths of innocents, but which is nonetheless a place of rosy, sweet, happy endings at the ends of storylines, because it's only important whether the "important" people survive? Does that explain Quentin's survival in 1897 and Beth's death?
It makes sense for an egotist like Roger to murder. Others would probably say, "Is even my survival worth this much?"
Ang at fire casting spell-- she sounds like she's trying to hypnotize the "ether" into altering its reality.
Just once, I want a life force subject to respond to the big electrical switch being turned on with a big, cartoony "Yeeeoooww!!"
Heatvamped Roger will be hard to interrogate or prosecute.