In a mixing bowl, combine the chopped spinach, feta cheese, cream cheese, green onions, garlic powder, and black pepper. Mix until well combined.
Lay one tortilla flat on a clean surface. Spread a quarter of the spinach and feta mixture evenly over the tortilla, leaving a small border around the edges.
Starting from one edge, tightly roll the tortilla into a log shape. Repeat with the remaining tortillas and filling.
Preheat your oven to 375°F (190°C). Line a baking sheet with parchment paper.
Slice each rolled tortilla into 1-inch thick pinwheels and place them cut side up on the prepared baking sheet.
Brush the tops lightly with olive oil and sprinkle with grated Parmesan cheese if using.
Bake in the preheated oven for 15-20 minutes, or until the pinwheels are golden and crispy.
Allow to cool slightly before serving.