In a small bowl, sprinkle the yeast over the warm milk with a pinch of sugar. Stir gently and let sit for 5–10 minutes until frothy.

In a large bowl, combine granulated sugar, melted butter, salt, eggs, and the yeast mixture, stirring until blended.

Gradually add flour, mixing until a soft dough forms. Knead the dough for about 5 minutes by hand or with a dough hook.

Gently fold in 1/2 cup rainbow sprinkles until evenly distributed throughout the dough.

Place the dough in a lightly oiled bowl, cover with a clean towel, and let it rise in a warm place until doubled, about 1 hour.

Punch down the dough and roll it out on a lightly floured surface into a 16×12-inch rectangle.

Spread the softened butter evenly over the dough, then sprinkle with brown sugar, cinnamon, and 1/4 cup rainbow sprinkles.

Tightly roll the dough from the long side into a log and cut it into 12 even rolls. Place them cut-side up in a greased 9×13-inch baking pan.

Cover the pan with a towel and let the rolls rise for 30 minutes while you preheat the oven to 350°F (175°C).

Bake the rolls for 20–25 minutes until they are puffed and golden brown on top.

While the rolls bake, whisk together powdered sugar, milk, and vanilla until smooth to make the icing.

Drizzle the icing over the warm rolls and finish with 2 tablespoons of rainbow sprinkles.