In a large bowl, combine 2 cups flour, brown sugar, yeast, cinnamon, and salt. Mix well.
Microwave milk and butter for about 30 seconds until warm and mostly melted. Let cool slightly if hot. Add milk mixture and mashed banana to the flour mixture.
Beat on low speed, then increase to high and mix for about 2 minutes until combined.
Add 1 cup flour and mix until combined. Gradually add the remaining flour until the dough pulls away from the bowl and forms a soft ball.
Transfer dough to a floured surface and knead for about 10 minutes until smooth and elastic.
Place dough in a lightly oiled bowl, cover, and let rise for 1 hour or until doubled in size.
Mix filling ingredients (brown sugar, cinnamon, salt) in a small bowl.
Roll dough into an 18 x 12-inch rectangle. Spread butter evenly and sprinkle cinnamon sugar mixture on top.
Roll tightly from the long side and pinch to seal. Cut into 12 rolls using floss or a sharp knife.
Place rolls in a parchment-lined 9 x 13-inch pan. Cover and let rise for another hour.
Bake at 350°F (175°C) for 30 minutes until golden and baked through. Cool slightly.
Beat frosting ingredients until light and fluffy. Spread over warm rolls and serve.