Finely dice the gherkins to 1. Cut apple into cubes and sprinkle with lemon juice. Put everything in a bowl, mix with yoghurt and season with salt and pepper. Clean, wash and slice the radishes.
Halve the rolls, spread with the salad cream and cover with lettuce leaves. Place roast beef, sprouts and radish slices on the salad leaves. Cut remaining cucumber into strips. Garnish the roll with onion rings and cucumber strips.