Combine active dry yeast, lukewarm water, and 2 teaspoons sugar; let sit 10 minutes until foamy.
In a mixing bowl, blend scalded milk, melted butter, mashed banana, remaining sugar, and salt on low speed until combined.
Add half the flour; mix until smooth. Stir in yeast mixture, then gradually add remaining flour until incorporated.
Knead dough on floured surface for 5 minutes. Place in greased bowl, cover, and let rise until doubled, about 1.5 hours.
Punch down dough and roll into a 16x24 inch rectangle on floured surface.
Spread softened butter evenly over dough. Mix brown sugar, cinnamon, and nutmeg; sprinkle over buttered surface.
Layer sliced bananas and chopped walnuts evenly over cinnamon sugar.
Roll dough tightly from long edge into a log; cut into 12 even slices.
Butter a 9x13-inch baking pan. Arrange slices close together. Cover and let rise until doubled, 1 to 1.5 hours.
Preheat oven to 375°F while rolls rise. Bake rolls 22-24 minutes until golden brown.
While baking, beat together cream cheese, softened butter, powdered sugar, vanilla extract, and salt. Add milk gradually for desired icing thickness.
Allow rolls to cool 10 minutes, then drizzle or spread icing on top. Serve warm.