Prepare the Dough:

1. Activate the yeast: In a small bowl, combine warm milk and 1 tsp of the granulated sugar. Sprinkle the yeast over the top and let sit for about 5-10 minutes until foamy.
2. Mix wet ingredients: In a large mixing bowl, combine mashed bananas, melted butter, remaining sugar, and egg. Mix until well combined.
3. Add yeast mixture: Pour the activated yeast mixture into the banana mixture and stir to combine.
4. Add dry ingredients: Add salt and 3 cups of flour, one cup at a time, mixing after each addition. The dough will be slightly sticky.
5. Knead the dough: Turn the dough out onto a floured surface. Knead for 5-8 minutes, adding the remaining 1/4 cup flour as needed, until the dough is smooth and elastic.
6. First rise: Place the dough in a greased bowl, cover with a clean kitchen towel, and let rise in a warm place for about 1 hour, or until doubled in size.

Make the Filling:

1. In a small bowl, mix together brown sugar and cinnamon until well combined.
2. Have your softened butter ready for spreading.

Assemble the Rolls:

1. Roll out the dough: After the dough has risen, punch it down and turn it out onto a lightly floured surface. Roll the dough into a large rectangle, approximately 16×12 inches.
2. Add the filling: Spread the softened butter evenly over the dough, leaving a 1/2-inch border around the edges. Sprinkle the cinnamon-sugar mixture evenly over the butter.
3. Roll and cut: Starting from the long edge, tightly roll the dough into a log. Using a sharp knife or unflavored dental floss, cut the log into 12 equal pieces, about 1 1/2 inches thick.
4. Second rise: Place the rolls in a greased 9×13 inch baking dish. Cover and let rise for another 30-45 minutes, until puffy.

Bake and Frost:

1. Preheat and bake: Preheat your oven to 350°F (175°C). Bake the rolls for 25-30 minutes, until golden brown.
2. Make the frosting: While the rolls are baking, beat together cream cheese and butter until smooth. Add powdered sugar and vanilla, and beat until creamy.
3. Apply frosting: Let the rolls cool slightly (about 10 minutes) before spreading the cream cheese frosting over the warm rolls.