Preheat your oven to 375°F. Grease your baking dish with the 15g of light butter.
In a large bowl, whisk together the bread flour, baking soda, baking powder, granular sweetener, and salt.
Add the Greek yogurt and egg yolk. Mix to a shaggy dough, then turn it out onto a floured surface and knead 1 to 2 minutes until smooth. It'll be sticky, so add a little flour as you go.
Roll the dough into a square about 1 inch thick. Yes, a full inch, that thickness is what gives you tall, bakery-style rolls.
Spread the softened light butter over the square, then sprinkle the brown sweetener and a generous dusting of cinnamon evenly across it.
Cut the square into 6 equal strips. Roll each strip up into a spiral to form a roll.
Place the 6 coils spiral-side up in your greased baking dish, leaving space between them. They will expand a lot in the oven.
Bake at 375°F for 22 to 25 minutes, until the tops are golden and set.
While they bake, beat the cream cheese, protein powder, vanilla, and sweetener together. Add water a splash at a time until it's spreadable. I used about 1/4 cup water. Spread the frosting over the rolls while they're still warm. Eat one immediately, those are the rules.