Combine flour, milk, sour cream, melted butter, salt, egg, yeast, and 1/3 cup of the granulated sugar in bowl of a stand mixer fitted with paddle attachment. Beat on medium speed until dough forms, 1 minute. Turn off mixer. Switch to dough hook attachment. Beat on medium speed until dough is smooth and elastic, about 6 minutes. (Dough should pull away from sides of bowl but stick to bottom.)

Spray a large bowl with cooking spray. Place dough in bowl, turning to coat all sides. Cover and let rise in a warm, draft-free place (about 75°F) until dough has doubled in size, about 1 hour and 30 minutes.

Lightly punch down dough. Roll dough out on a lightly floured surface into a 19- x 13-inch rectangle. Spread softened butter over dough.

Stir together 3 tablespoons of the orange zest and remaining 2/3 cup granulated sugar. Sprinkle sugar mixture over buttered dough, gently pressing to adhere. Starting with 1 long side, roll dough into a log, and pinch seam to seal. Turn log seam side down, and cut into 12 rolls. 

Spray a 12-cup muffin pan with cooking spray. Using your thumb, push upward slightly beneath bottom center of each roll, and place rolls into prepared pan. Cover with plastic wrap, and let rise in a warm, draft-free place (about 75°F) until almost doubled in size, 45 minutes.

Preheat oven to 350°F. Uncover rolls. Bake until golden brown and cooked through, about 20 minutes. Transfer pan to a wire rack; let stand in pan 5 minutes. Remove rolls to wire rack.

Whisk together powdered sugar, 3 tablespoons of the orange juice, and remaining 1 teaspoon orange zest in a bowl, adding remaining 1 tablespoon juice 1 teaspoon at a time, if needed, for desired consistency. Drizzle glaze over warm rolls.