1. In a large bowl or a bowl of a stand mixer, combine the warm milk with yeast and 1 teaspoon of sugar. Stir to combine. Let sit for about 10-15 minutes until the mixture becomes foamy.
2. Add the remaining sugar, salt, vanilla, and melted butter. Mix until well combined.
3. Add half of the flour. Change to a dough hook and mix on low until smooth. Add the mashed banana and mix on low until combined. Slowly add the remaining flour until fully incorporated. Knead for another 5 minutes until the dough is smooth and not sticky.
4. Place the dough into a large well-greased bowl, cover with plastic wrap. Let the dough rise in a warm draft-free place until it has doubled, about 1 hour.
5. Grease a large baking dish (9×13 inch). Set aside.
6. Transfer the dough to a lightly floured work surface. Using a rolling pin, roll the dough out into the shape of a rectangle. Spread the softened butter over the surface of the dough and top evenly with sugar, cinnamon, and nuts. Layer evenly sliced bananas.
7. Roll up the dough into a long tight log. Pinch to seal the edges. Gently squeeze to compact the log of dough.
8. Cut the log into 12 equal pieces. You can use dental floss or a thin thread. Place the rolls into the prepared pan. Cover it with a towel and let proof for about 30 minutes for the second time.
9. Preheat oven to 350°F. Bake the rolls for 30-35 minutes until the tops start turning golden-brown. Remove from the oven and allow to cool slightly.
10. Meanwhile, make the frosting. Add the cream cheese and butter to a mixing bowl. Mix on medium speed until light and fluffy. Mix in the powdered sugar and vanilla. Beat until smooth and well combined.
11. Spread the frosting over the warm rolls. Top with walnuts and cinnamon.