In a large mixing bowl, combine ½ cup active sourdough starter, ½ cup pumpkin purée,1 large egg, ⅓ cup granulated sugar, 1 teaspoon vanilla extract and melted 4 tablespoons unsalted butter. Stir in3 ½ cups all-purpose flour, 1 ½ teaspoons pumpkin pie spice and 1 teaspoon salt until a dough forms. Knead until smooth, then cover and let it rest for 4–6 hours or overnight until doubled in size.
In a small bowl, mix softened butter, ½ cup brown sugar, and 1 tablespoon ground cinnamon until well combined. Set aside.
On a lightly floured surface, roll the dough into a large rectangle, about ¼-inch thick. Spread the cinnamon-sugar filling evenly over the dough, leaving a ½-inch border.
Starting from the long side, tightly roll the dough into a log. Slice into 8–10 even rolls using a sharp knife or dental floss.
Place the rolls into a greased or parchment-lined baking dish. Cover loosely and let rise at room temperature for 1–2 hours until puffy.
Preheat your oven to 350°F (175°C). Bake the rolls for 25–30 minutes or until golden brown and cooked through.
While the rolls bake, whisk together 1 cup powdered sugar, 2 to 3 tablespoons milk, and vanilla extract to make a smooth glaze.
Drizzle the glaze over warm rolls. Serve immediately and enjoy the soft, spiced, sourdough-infused treat!