Wash parsley and shake dry, pluck off leaves and chop finely. Wash lemons hot, dry and finely grate the zest of 1 lemon. Mix capers, parsley, lemon peel, 2 tbsp. oil and breadcrumbs. Season with salt and pepper.
Dab schnitzel dry, cut in half crosswise and tap flatter between a cut open freezer bag. Season schnitzel with salt and pepper. 2. cut lemon in half lengthwise. Set 1 half aside, halve the other half again lengthwise. Cut the quarters into 16 slices.
Preheat oven (electric cooker: 150 °C/circulating air: 130 °C/gas: see manufacturer). Spread approx. 1 teaspoon caper mixture on each cutlet. Roll up the cutlets, folding the long sides inwards by approx. 1⁄2 cm. Put lemon wedges with the roulades on 16 wooden skewers.
Heat 3 tablespoons of oil bit by bit in a large frying pan. Fry the skewers in it in portions all around for 4-5 minutes. Place the skewers on a baking tray and continue to fry in the hot oven for about 10 minutes.
In the meantime drain the tuna. Peel and chop the garlic. Squeeze the remaining lemon half. Finely mash the tuna, mayonnaise and garlic. Season to taste with salt, pepper and lemon juice. Serve the dip with the roulade skewers.