Exactly. Like all German warships, GZ had to pass the Kiel Canal. However, with her huge hull she posed a large area of attack for side winds and her maximum speed in the canal (9kn) wasn't enough to compensate. These Voith-Schneider propellors were there to keep her steady. They were also powerful enough to accelrate the whole carrier alone to a whopping 4kn, given there was no current, wind or any form of rough sea... (The propellors were also completely retractable).
I don't think there was ever a full carrier conversion planned for Roon, as far as I know, so there are no plans for me (at the moment). Currently, I'm trying to get the Hipper-class done.
Wow, those are pretty handy.
And about the full Roon conversion, perhaps that can be left for the AU thread.