• To the bowl of a stand mixer fitted with the paddle attachment, add warm milk, 1 tablespoon of granulated sugar, and yeast. Mix briefly, then let the mixture sit for about 5 minutes until foamy.
• Add eggs, butter, the remaining 4 tablespoons of sugar, all-purpose flour, bread flour, and salt. Switch to the dough hook attachment. Mix on low speed to combine.
• Continue kneading on medium speed until the dough is smooth, about 5 minutes.
• Spray a medium bowl with nonstick cooking spray. Place the dough into the bowl, rotating it to grease all sides. Cover with a towel or plastic wrap. Let it rise in a warm area until doubled in size, 1-2 hours.
• Once the dough has doubled in size, place it onto a floured counter or work surface. Roll the dough into a 10×15-inch rectangle, about ¼-inch thick.

Filling

• In a small bowl, combine the butter, brown sugar, granulated sugar, flour, vanilla, and salt.
• Evenly spread the butter mixture over the dough, making sure it covers the entire surface.
• Sprinkle the entire surface with sprinkles.

Assembly

• Spray a 9×9-inch baking dish with nonstick cooking spray.
• Starting on the long edge of the dough, tightly roll it up (like a log or cylinder).
• Using a very sharp knife, evenly cut the log into 9 rolls. Place them into the prepared baking dish, filling side up.
• Cover with plastic wrap. Let rise in a warm place until doubled, about an hour.

Bake

• Preheat oven to 325°F.
• Bake for 35-40 minutes, or until lightly golden on the edges and done in the middle.
• When the rolls are almost done baking, make the frosting.

Frosting

• To the bowl of a stand mixer with the paddle attachment, add cream cheese, butter, confectioners' sugar, vanilla, and salt. Mix on low just to combine.
• Once the ingredients are all incorporated and smooth, switch to the whisk attachment. Mix on high for 4-5 minutes until light and fluffy.
• Immediately frost the rolls while still warm.
• Finish with a sprinkle of rainbow sprinkles on top.