Line a baking sheet pan with parchment paper. Set aside.
In a small mixing bowl, combine warmed milk, yeast and granulated sugar. Stir gently, once or twice, just to combine. Set aside for about 3-5min and allow to bloom - mixture will become bubbly and frothy.
In a large mixing bowl combine mashed banana, egg, and melted butter. Mix to combine. Next add flour, cinnamon and salt. Add the yeast mixture and stir with a wooden spoon until a dough ball begins to form.
Turn dough out onto a floured surface and knead by hand until the dough is smooth and somewhat elastic (about 5-7min). (You can also use a stand mixer with a dough hook attachment, if you prefer).
Transfer the dough ball to a greased mixing bowl and cover with a warm towel. Allow dough to rise 1 hour, or until doubled in bulk.* (See Notes)
After the dough has doubled in size, transfer dough to a well-floured surface and roll out into a 12x16 rectangle. Spread softened butter evenly over the dough.
In a small mixing bowl, combine dark brown sugar and cinnamon. Using your hands, evenly distribute the mixture over the dough and rub it into the butter. Then, sprinkle with toasted chopped pecans.
Arrange the dough so the long edge is facing you. Find the midpoint of the long edge of the dough. Using a large chef's knife or pizza cutter, slice the rectangle into two halves from this point. Then cut each resulting rectangle in half again, in the the same manner. Repeat until there are 8 strips of dough. (If you'd like more, smaller rolls, cut into thinner strips).
Beginning at the end closest to you, start tightly rolling individual rolls with each strip of dough (like rolling crescent rolls). Place each roll on a parchment lined baking sheet - leave about 1-2 inches of space between each roll. Cover rolls with a warm towel and place in a draft free space for a second rise (about 20-30 minutes).
Preheat Oven to 350°F while the rolls rise.
Bake the cinnamon rolls until the edges are lightly browned. You can also check if they are finished baking by inserting an instant-read thermometer into the center of a roll - the internal temperature needs to be around 190°F.