Toast pine nuts in a small pan over medium heat until golden. Place spinach, arugula, garlic, cheese, salt, pepper, nutmeg, and toasted nuts in a food processor. Pulse the filling into a paste. Taste and adjust seasonings. Remove 1/2 cup of filling paste to a bowl and stir in extra-virgin olive oil to loosen it. Reserve remaining filling in processor bowl.
Place steaks between two layers of waxed paper. Pound steaks with meat mallet until they are ¼ inch thick. Season each steak with salt and pepper on both sides. Cover each steak with a thin layer of filling and top with roasted red peppers. Roll steaks tightly and cut each steak in half across.
Secure braciole with a carefully placed skewer and set six pinwheels on a baking sheet. Drizzle with extra-virgin oil and roast 12 to 15 minutes. Remove skewers and transfer pinwheels to dinner plates. Top each with a generous portion of reserved sauce made from filling and extra-virgin olive oil.
