Cut the potatoes into thin slices and put them in a bowl with water.
Drain them on paper towels.
Put them on a sheet pan covered by parchment paper. Oil the potatoes, with extra virgin olive oil, and flavour with salt, freshly ground black pepper and rosemary.
Bake them in the hot oven for about 10 minutes at 200°C, until when they are slightly golden brown.
In the meantime, cut the mozzarella cheese into small pieces.
Take the potatoes out from the oven and alternate them with the layers of slices of bologna and mozzarella.
Bake again for a few minutes to melt the mozzarella cheese and serve immediately.