01 - Combine flour, sugar, yeast, and salt in a large mixing bowl.
02 - Add warm milk, melted butter, and egg to dry ingredients. Mix until sticky dough forms.
03 - Knead dough on floured surface for 8-10 minutes until smooth and elastic, or use stand mixer with dough hook.
04 - Place dough in greased bowl, cover, and let rise in warm place until doubled, approximately 1 hour.
05 - Combine sugar and lemon zest in small bowl, rubbing together to release citrus oils.
06 - Roll dough on floured surface into 12x16-inch rectangle.
07 - Spread softened butter over dough. Sprinkle evenly with lemon sugar and scatter blueberries on top.
08 - Starting from long edge, tightly roll dough into log. Slice into 12 equal pieces.
09 - Arrange rolls in greased 9x13-inch baking dish. Cover and let rise 45 minutes until puffy.
10 - Preheat oven to 350°F.
11 - Bake rolls for 22-25 minutes until golden brown.
12 - Whisk together powdered sugar, milk, and vanilla extract until smooth.
13 - Drizzle vanilla icing over warm rolls. Serve immediately.