Toni,

I am German. I get the beef for my rouleans (Rouladen) precut at my butcher's. They are 3/8 inches thick (cut against the grain) from the sirloin, about 4 x 12 inches in size. If you can get a similarily tender and large cut you might try my recipe:

Takes about 90 minutes

2 tbsp vegetable oil
4 rouleans
salt pepper
2 tsp Dijon-style mustard
4 - 8 thin slices of smoked ham (enough to cover the rouleans)
1 1/2 cups finely chopped onions
3/4 cup finely chopped drained dill pickle
about 1 cup beef stock
2 tsp flour

thread (no plastic!) to bind rouleans Dry rouleans on paper towels and put side by side on worktop. Salt and pepper to taste.
Spread thin and evenly with mustard,leaving out an inch at one of the small sides.
Put the ham in one layer on the rouleans, cut off overlapping parts.
Combine half of the onion and all of the pickle and distribute evenly on rouleans, leaving 1/2 inch on three sides, 1 inch on one small side.
Fold the long sides in 1/2 inch ( so the filling won't pour out), and roll the rouleans up from the small side spread with mustard.
Now bind the beef firmly crosswise like a parcel. You can secure the seam additionally with an inserted toothpick.
Salt and pepper on the outside.

Heat oil in a casserole just large enough to hold the rouleans over medium-high heat. Add rouleans seamside down and brown nicely on all sides, about 10 minutes.
Remove from the casserole and add remaining onions. Cook stirring until brown.
Add hot! beef broth and cook one minute,stirring. Broth should be nicely brown.
Add rouleans. Broth should cover them by half. Spoon some broth over rouleans and cover casserole. Reduce heat to low. Rouleans should constantly simmer covered for 45 to 60 minutes. Spoon with cooking liquid every 15 minutes, turn once.
When done, remove rouleans from broth and keep warm, covered.
Make sauce. Wisk flour with a little cold water and pour into broth, stirring constantly. Boil for 5 minutes. Taste with salt and pepper.
To serve: Remove thread and toothpicks. Cut roulean once diagonally. Put on a plate and spoon some of the sauce over it. Serve with steamed green beans and boiled potatoes, along with remaining sauce.

Guten Appetit.