According to the wikipedia, Rouladen are "bacon, onions, mustard and pickles wrapped in thinly sliced beef which is then cooked". This is basically correct, but tells you nothing about the taste and texture. Let alone the sauce. And of course, there are millions of recipes - almost every German hausfrau has their own. I, for example, like to keep the onions in the sauce, not in the rolls. And the sauce is based on red wine, which I happen to like very much and have known since childhood.
My mother-in-law on the other hand, makes the sauce with tons of mustard. And my grandmother used to make a simple brown sauce. Over the years, I have developed quite a mixture of all of those recipes. Serve it with any starch you like, but I prefer either mashed potatoes or spaetzle.
