Strtings

Doe's anybody knwo what kind of strings Roger uses on his bass?

I can sincerely say no.

uh...bass strings.

They are Rotosound strings.
It's a very good brand of handmade strings made in the UK, I didn't know they were the ones Rog uses until I bought them for my bass player and we noticed that there were some writings explaining that they were the strings used by Waters, John Paul Jones, Adam Clayton, I believe also John Entwistle but I'm not sure, and some others.

Are they just rotosound? No special gauge or anything?

I don't know for sure what gauge Rog is more confident with, y'know it only said that it was the right brand, but to know the exact gauge you'd have to ask someone who works with him, the guy in his fave instruments shop or himself!
Anyway I seem to remember the ones I bought had the G of a good 46 and they sound great.
Remember that Rog usually works with 2 basses (at least on stage, I assume him to own many more), one with standard tuning and the other on a drop-D tuning, which means that you have to get your low E tuned down to a D, as heard a lot on the wall (The Happiest Days of Our Lives, ABITW 2 & 3, What Shall We Do Now, Run Like Hell etc), so for that tuned down E string I'd suggest a custom, thicker gauge.