Preheat your oven to 375°F (190°C). Grease a 9x13 inch baking pan.
In a large bowl, whisk together the flour, granulated sugar, baking powder, and salt.
In a separate bowl, whisk together the milk and melted butter.
Pour the wet ingredients into the dry ingredients and stir until just combined. The dough will be sticky.
Turn the dough out onto a lightly floured surface and knead for about 1-2 minutes until it's smooth. It will still be a bit sticky.
Roll the dough into a 12x18 inch rectangle.
In a small bowl, combine the brown sugar and cinnamon. Sprinkle this mixture evenly over the rolled-out dough. Spread the softened butter over the sugar and cinnamon mixture.
Starting from one of the longer sides, tightly roll up the dough.
Cut the roll into 12 equal slices. Place the slices cut-side up in the prepared baking pan.
Bake for 15-18 minutes, or until golden brown.
While the rolls are baking, prepare the frosting. In a medium bowl, beat the cream cheese and butter until smooth. Add the powdered sugar, milk, and vanilla extract, and beat until the frosting is light and fluffy.