Preheat Oven: Preheat your oven to 200°C (400°F).

Prepare the Spinach Mixture: In a large skillet, heat olive oil over medium heat. Add minced garlic and sauté for about 1 minute until fragrant. Add the chopped spinach and cook until wilted, about 3-4 minutes. Remove from heat and let it cool slightly. Drain excess moisture from the spinach by pressing with a spoon or using a clean kitchen towel.

Mix the Cheeses: In a large mixing bowl, combine ricotta cheese, cream cheese, and crumbled feta cheese. Add the cooled spinach to the cheese mixture. Season with salt, black pepper, and a pinch of nutmeg if using. Mix well until all ingredients are evenly combined.

Assemble the Roll: On a lightly floured surface, roll out the puff pastry sheet into a rectangle, about 25×30 cm (10×12 inches). Spread the spinach and cheese mixture evenly over the pastry, leaving a 2 cm (1 inch) border around the edges. Carefully roll the pastry from one side to the other, into a log shape. Pinch the edges to seal the roll closed.

Bake the Roll: Place the roll seam-side down on a baking sheet lined with parchment paper. Brush the top and sides of the roll with beaten egg for a golden finish. Bake in the preheated oven for 25-30 minutes, or until the pastry is puffed and golden brown.

Serving: Remove from the oven and let it cool slightly. Garnish with freshly chopped parsley. Slice and serve warm.