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