Over a lasagna sheet, place the ham and cheese slices, oregano to taste, roll the dough by pressing on it to prevent it from opening while we cut it. Cut this log into 3 equal pieces, repeat this process with the rest of the lasagna sheets.
Transfer these rolls to a baking dish.
In a pan, sauté the onion and the garlic, add the tomato sauce, the salt and the water, mix well and let it cook for 3 minutes.
Pour the sauce over the roll ups into the baking dish, cover and close the dish well with aluminum foil and bake in a preheated oven at 180°C (356°F) for 40 minutes, remove the aluminum foil and bake for another 20 minutes.