Preheat the oven to 400°F; if you're using a baking steel/stone to bake the pizza, make sure it's in the oven. Line a rimmed baking sheet with parchment paper.
Arrange the sliced pumpkin on the prepared baking sheet, drizzle with olive oil, salt, and pepper, and toss to coat. Make sure the pumpkin slices are in a single layer, then transfer to the oven and roast for 20 minutes or until fork tender. Remove from the oven and set aside to cool slightly.
Increase the oven temperature to 500°F (if using a baking sheet) or as high as it will go (if using a baking stone/steel).
Stretch or roll out your dough to a 12-inch circle, then transfer it to an oiled baking sheet or a lightly floured pizza peel (if using a baking stone/steel).
Spoon the marinara sauce onto the dough and spread it out evenly, leaving a ½-inch border of dough all around. Scatter on the shredded kale and sliced sun-dried tomatoes, and arrange the pumpkin slices on top, being careful not to overcrowd the pizza. (If you have more pumpkin slices than you need, just pack up the extras up for another meal or snack.) Finish with the cheese, a generous pinch of salt, a grind or two of black pepper, and a light sprinkle of cinnamon.
Transfer the pizza to the oven and bake until the crust is golden and the cheese has browned in spots, 8 to 10 minutes on the baking sheet, 6 to 8 minutes on the baking stone/steel.
Take the pizza out of the oven. Slice and serve.