Advice on meat cuts for German rouladen
The meat for rouladen is cut from the upper part of the hind legs of the cow, or Oberschale.  

You definitely don't pound rouladen; pounded meat tends to re-contract somewhat under heat, and this unacceptable in this case. I don't know how to cut it that way at home. In Germany, the butcher sells the meat pre-cut to the correct size. I guess that he "peels" it from the cut with a sharp knife. As far as I remember, it isn't cut across the grain like steaks. And it has to be very thin, from memory I would say that 1/7 inch thickness is normal. On this site, you can see some close-ups of the raw meat, maybe the butcher can recognize how to cut it from that. (Don't worry about the text, the recipe is far from traditional. I only gave it as a good illustration of the raw cuts). 

Also, rouladen are supposed to be tender. If possible, get veal. If not, young bull's meat is better than the normal beef used for steaks.