Adjust the oven rack to the middle position and heat the oven to 400°F. Line a rimmed baking sheet with parchment paper. Mix the spinach, ricotta, feta, scallions, raisins, pine nuts, lemon juice, oregano, garlic, and nutmeg in a large bowl, seasoning with salt and pepper to taste.

Layer the phyllo sheets on a clean counter, coating each sheet thoroughly with olive oil spray to ensure a light, flaky finish. Mound the spinach mixture into a narrow log along the bottom edge of the phyllo, leaving a 2-inch border at the bottom and a half-inch border on the sides.

Fold the bottom edge of the dough over the filling, then continue to roll the dough into a tight log, leaving the ends open. Transfer the strudel seam-side down to the prepared baking sheet. Lightly spray with olive oil and cut four diagonal vents across the top to allow steam to escape during baking.

Bake until the pastry is golden brown and crisp, about 20 minutes, rotating the baking sheet halfway through for even color. Let the strudel cool on the baking sheet for 5 minutes to help the filling set before slicing. Serve warm, while the crust is still shatteringly crisp.