Place a pizza stone on the bottom rack of the oven and preheat to 425 degrees.
Heat a large skillet to medium and add onion. Cook for 8 minutes. Add spinach or kale and cook until wilted. Add garlic and cook for 1 more minute. Transfer to a medium bowl and toss with roasted red peppers.
Roll pizza crust into a large rectangle on a sheet of parchment paper, using gluten free flour as needed to avoid sticking. Spread vegetable mixture evenly, leaving a 1 inch border. Top with mozzarella and ½ of the Parmesan and sprinkle with oregano and red chili flakes.
Fold the short ends of the dough in and roll the long end, using the parchment paper as needed to assist in rolling. Sprinkle with remaining Parmesan. Use a pizza peel or back of a cookie sheet, transfer parchment paper to your pizza stone.
Bake for 25 to 30 minutes, or until golden brown. Serve warm with marinara for dipping.