Brush the roulade slices with mustard, sprinkle with pepper and (if you like) flavor. Cut the onion into rings, cut the gherkins lengthways into slices and cover the roulade slices with them. Roll up the slices and wrap them with twine. Chill the roulades in sour cream and wine vinegar for 1 to 3 days, turning them several times.
Salt the drained roulades, turn them in the flour mixed with paprika and fry them until brown. Add the tomato paste and fry briefly. Pour in the meat stock and half of the marinade. Let simmer on low heat for 1 hour.
Whisk the remaining marinade with flour, stir into the sauce and bring to the boil.