Rouladen is the German version of the French Roulade. The latter is a French term for slices of meat rolled around a filling. It's typically browned before being braised or baked.
Two popular German Rouladens include Rindsrouladen which is slices of beef rolled around a pickle, onion, and bacon mixture, and Kohlrouladen which is made of cabbage leaves rolled around a ground beef mixture.