In a large, microwave-proof bowl, combine the milk and melted butter. Microwave for 40 seconds, until the milk mixture reaches 110˚F (45˚C). Add the yeast, then let sit for 10 minutes.
Add the granulated sugar, salt, mashed bananas and stir.
Add 3½ cups (435 g) of flour, ½ cup (60 g) at a time, stirring between each addition.
Transfer the dough to a floured surface and knead for 3 minutes, adding more flour ¼ cup (30 g) at a time if the dough is sticking to your hands or the surface. Form the dough into a ball.
Add the oil to clean large bowl and place the dough in the bowl. Cover with a kitchen towel and let rise for in the refrigerator for at least 3 hours, or overnight, until doubled in size.
Once the dough has risen, roll it out to a ¼-inch-thick (6-mm) rectangle about 18x12 inches (20x30 cm).
Make the filling by mixing the melted butter, granulated sugar, and cinnamon together in a small bowl.
Spread the filling evenly over the dough. Roll up the dough and slice into 15 1½-inch (4-cm) thick slices (discard the ends).
Make the caramel sauce: In a small saucepan over medium heat, combine the butter, brown sugar, salt, vanilla, and honey. Keep stirring to prevent the sugar from sticking to the pan. Bring to a gentle boil, then remove the pan from the heat.
Pour the caramel sauce into a 9x12-inch (23x30-cm) baking dish and sprinkle the walnuts on top of sauce. Arrange the rolls in the dish so there are 3 rows of 5 rolls.
Cover with plastic wrap and let the rolls rise for 15 minutes, in a warm place.
Preheat the oven to 350˚F (180˚C).
Remove the plastic wrap and bake the cinnamon rolls for 40 minutes, or until light golden brown.
Let cool for 20 minutes, then invert the rolls onto a serving platter. Leftover cinnamon rolls can be stored up to 5 days in the refrigerator. Reheat in the microwave or oven.