This recipe will make 12 medium size rolls that you can bake in a 9 x 13 pan or bake individually on parchment on a baking sheet. For something like this, adding some whole wheat to the dough helps make for a richer, more complex flavor and there is plenty of sugar to balance any of the whole wheat's bitterness. I have tried a number of ingredients to make for a softer dough. Oat flour is just too sticky, corn starch to starchy. Mashed potatoes seem like the best dough softener.
I think the best filling incorporates a bit of invert sugar (corn syrup or agave) and to help keep it from running out of the rolls, I add a bit of corn starch. I haven't really found butter to help the filling much and now leave it out of the filling. If you have an extremely sharp or fresh Vietnamese cinnamon, you might want to back the amount of cinnamon down to 2 tsp. Finally, adding cream cheese to the icing helps balance the extreme sweetness found elsewhere in the roll.