Preheat the oven to 170 C
Beat the eggs white until they are stiff. Add the vinegar and beat for another 30 seconds. Use a blender of food processor to chop the rocket very finely. Fold the rocket and grated parmesan through the egg whites.
Line a shallow baking tray/roulade tin with baking paper and spread the egg and rocket mixture across the paper. Smooth it out with a flat spatula.
Place in the oven for 20 minutes.
While the roulade is baking, blend the tuna together with the shallots, capers, mayonnaise and pepper.
Remove the roulade from the oven and allow it to cool slightly. Spread the tuna mixture across the top of the roulade then carefully roll it up to form a log shape.
Slice and serve