01 - Combine flour, sugar, yeast, and salt in a large mixing bowl. Add warm milk, melted butter, and egg. Mix until a sticky dough forms, then knead on a floured surface for 8-10 minutes until smooth and elastic. A stand mixer with dough hook may be used instead.
02 - Place dough in a greased bowl, cover with plastic wrap or a clean towel, and let rise in a warm, draft-free area until doubled in volume, approximately 1 hour.
03 - While dough rises, combine granulated sugar and lemon zest in a small bowl. Rub together with fingertips to release the citrus oils.
04 - Punch down risen dough and roll out on a floured surface to a 12x16-inch rectangle. Spread softened butter evenly over the dough, leaving a 1-inch border. Sprinkle with lemon sugar mixture and distribute blueberries across the surface.
05 - Starting from one long edge, roll dough tightly into a log. Use a sharp knife or unflavored dental floss to slice into 12 equal pieces, approximately 1 1/2 inches thick.
06 - Arrange rolls cut-side up in a greased 9x13-inch baking dish. Cover and let rise in a warm place for 45 minutes until puffy and nearly doubled.
07 - Preheat oven to 350°F. Bake rolls for 22-25 minutes until golden brown and cooked through. The internal temperature should reach 190°F when fully baked.
08 - While rolls bake, whisk together powdered sugar, milk, and vanilla extract until smooth and creamy. For additional lemon flavor, incorporate 1 tablespoon fresh lemon juice.
09 - Drizzle vanilla icing over warm rolls immediately after removing from the oven. Allow to set for 5 minutes before serving. Best enjoyed fresh and warm.