Preheat the oven to 200°C or 392°F. I baked it using the bottom and top (fan-assisted) settings.
Prepare the roasted pumpkin with oregano according to the instructions provided here. While the pumpkin is baking, prepare the meat filling. To do this, pour the frozen spinach into a saucepan. Add a large pinch of salt and a little water. Steam it, then put it in a strainer and drain it. Once cooled, squeeze it further with your palm to remove any excess liquid, as this will make the filling too runny. When it has stopped releasing liquid, place it in a mixing bowl. Season with salt and mix in the nutmeg, feta cheese, cream cheese, and 2 mandarin oranges, cut into pieces and diced. When ready, place in the refrigerator while you prepare the meat.
Clean the meat and cut it into large slices. Spread out some baking paper, place the meat on it, season with salt and pepper, then pound it thin. Do this on both sides.
Take out the filling and spread it over the meat slices. Spread evenly, then roll up the meat. Place the stuffed chicken rolls in a heatproof dish. Cover the dish with aluminum foil.
Place in an oven preheated to 200°C or 392°F for 40 minutes, baking on the bottom and top racks.
After 40 minutes, remove the aluminum foil and roast the top of the chicken for another 15 minutes. When ready, let the meat rest for 15 minutes in the closed oven before serving.
Place the meat slices on a plate and pile the pumpkin cubes on top. Sprinkle with feta cheese. I calculated 2 servings of oregano pumpkin per person.