The piadina kebab is the spit-roasted döner filling carried in a Romagnola round instead of flatbread or a roll, and the carrier is the whole point. Meat stacked on a vertical spit, seasoned and pressed into a cone, is roasted as it turns and shaved off in thin strips to order, then loaded into a piadina with shredded salad and sauce and folded around the lot. The defining fact is that the round is being asked to do a job it was not built for: hold a hot, loose, fatty filling that wants to spill. The piadina answers because it is pliable enough to wrap tight and strong enough not to tear, and because warmed on the griddle it grips the strips rather than sliding off them. The meat brings the heat and the fat, the salad and sauce bring the cut and the moisture, and the fold is what keeps a spill-prone filling in one hand.
The craft is controlling a wet filling inside a thin bread. The shaved meat comes off the spit slick with its own rendered fat and juice, so the round is often passed back over the testo to firm and warm it before filling, which makes it grip and keeps it from going through on the first bite. The salad is shredded fine and the sauce, a cool white yoghurt-based one or a hot red, is portioned to season and to cut the fat without flooding the seam, and the whole load is judged so the round can still fold shut around it. It is assembled and handed over at once and eaten standing, because a piadina kebab that waits goes soggy and cold and loses the contrast of hot meat against cool sauce that makes it worth eating. A sloppy build overfills a cold round and sheds meat and sauce out the open end.
The variations are mostly the carrier and the heat of the sauce. There is the same filling packed into a split roll instead of a fold, the spiced red sauce against the cool white one, the all-salad vegetarian build with falafel in place of the spit meat, and the wider modern counter of made-to-order street folds this shares a griddle with. Each of those is the same spit filling with one decision changed, and each deserves its own article rather than being crowded in here.