Toast bread until golden brown. Mix quark and horseradish, season with salt and pepper. Wash the rocket and dab dry. Clean and wash radishes, dab dry and cut into slices.
Put a slice aside for garnishing. Halve the remaining slices and sprinkle on the roast beef slices. Cover each roast beef with a leaf of rocket and roll up. Spread horseradish cream on the bread.
Put the rolls on top. Garnish bread with remaining rocket and radish slice.