Rouladen is a roll of thinly sliced meat, usually beef, that has some kind of stuffing inside the roll. The stuffing can be just about anything imaginable but the common thread is that the meat has usually been cooked and/or marinated in a vinegar or wine solution much like Sauerbraten.
Google.de brings up this yummy-looking recipe - click through for a photo.
www.marions-kochbuch.de
zymurgist