Does anyone know where I can get a hold of the font used in Rogue Traderfor all of the chapter headings and such?

Nope but try here, literally hundreds of different ones:

http://www.dafont.com/theme.php?cat=115

If it's like Dark Heresy, it's a font owned by GW, so it won't be publicly available, at least legally.

It's a font called REQUIEM-Inquisitor. GW propietary, unfortunately.