Dough: Whisk together 2 1/2 cups flour, sugar, salt, baking powder, and baking soda. Stir buttermilk and melted butter into dry mix, then transfer to a well-floured surface and knead a few times, until blended. If dough sticks easily to hands, add a touch more flour. Roll dough into a 1/2 to 1/4 inch thick rectangle.
Roll: Combine filling ingredients and sprinkle evenly over dough, leaving 1 inch on one of the long sides free. Starting at the long side opposite to the free border, roll the dough tightly, gently pinching to seal. Use floss or a sharp knife to cut the dough into 8 even segments.
Bake: Place rolls in a parchment paper-lined or well-greased baking sheet, leaving some wiggle room between rolls (they'll grow!)* Bake at 425 degrees F (218 C) for 20 to 25 minutes, until tops are golden brown.
Serve: Combine all icing ingredients and drizzle over warm rolls.
*At this point you can cover and leave these in the fridge overnight for baking in the morning!