When I run Rogue Trader, I bring all of my books on my laptop in PDF form. Same for Pathfinder.
When I was playing Pathfinder, I only brought my character PDF and the SRD reference App that I had on my tablet, my dice, and a tiny little notebook for notes and such.
When I have run Pathfinder, same as Rogue Trader, with all of the books on my lap top, my GM screen, and my tablet to use for my die roller (much quicker to tap 10d6 than to get 10 six sided dice out, roll them, and count them up).
I also tend to read most of my rulebooks on my tablet in PDF form, because I can take them with and read them at lunchtime and when I'm out and about when I couldn't lug a full sized book with me.