Heat broiler, with rack in top position. Place pork, turkey, spinach, breadcrumbs, egg whites, oregano, 1 1/2 teaspoons salt, and 1/2 teaspoon pepper in a large bowl. With your hands, mix to combine; roll into forty 1-inch meatballs. Arrange meatballs on a rimmed baking sheet. Lightly coat with cooking spray. Broil until golden brown, 10 minutes, rotating sheet halfway through.
In a large heavy pot, heat oil over medium. Add onion and garlic and cook, stirring occasionally, until onion is translucent, 6 minutes. Add tomatoes and Sriracha and bring to a simmer. Add meatballs and simmer 10 minutes. (To store, let cool, then refrigerate in an airtight container, up to 1 week, or freeze, up to 3 months.)
In a large pot of boiling salted water, cook pasta according to package instructions. Drain pasta, add to pot with sauce and meatballs, and toss to coat. Sprinkle with parsley and serve.
A small spring-loaded scoop makes forming perfect meatballs quick and easy.