Prepare the Filling:

1. Cook the Spinach: Heat olive oil in a large skillet over medium heat. Add the chopped onion and sauté until soft and translucent, about 5 minutes. Stir in the garlic and cook for an additional minute.
2. Wilt the Spinach: Add the fresh spinach to the skillet and cook until wilted, stirring frequently. If using frozen spinach, ensure it’s thoroughly thawed and drained before adding it to the skillet.
3. Remove Excess Moisture: Transfer the spinach mixture to a colander or clean kitchen towel and press out any excess liquid to prevent a soggy filling.
4. Mix the Filling: In a large bowl, combine the spinach mixture, feta cheese, ricotta cheese (if using), dill, beaten egg, salt, and pepper. Mix until well combined.

Assemble the Rolls:

5. Prepare the Phyllo Dough: Lay one sheet of phyllo dough on a clean, flat surface. Cover the remaining sheets with a damp kitchen towel to prevent them from drying out.
6. Brush with Butter: Lightly brush the phyllo sheet with melted butter. Place another sheet on top and brush again. Repeat until you have a stack of three sheets.
7. Add Filling: Spoon 2-3 tablespoons of the spinach filling along one short edge of the phyllo stack, leaving a 1-inch border on each side.
8. Roll and Seal: Fold in the sides and roll the phyllo tightly, starting from the edge with the filling. Place the roll seam-side down on a baking sheet lined with parchment paper. Repeat with the remaining phyllo and filling.
9. Brush and Garnish: Brush the tops of the rolls with melted butter and sprinkle with sesame or nigella seeds if desired.

Bake:

10. Preheat the Oven: Preheat your oven to 375°F (190°C).
11. Bake: Bake the rolls for 20-25 minutes, or until golden brown and crispy.
12. Cool Slightly: Allow the rolls to cool for a few minutes before serving.