Start by peeling the bananas and cut them into thin slices.
Then, squeeze the juice of a lemon over all of them.
Place the banana slices on the sheet of puff pastry, lining up the slices and leaving a space between them and gently roll up the pastry.
Now, using a knife, cut this log into about 2-finger thick round slices.
Transfer all these slices to a large non-stick baking sheet or lined with parchment paper.
Then, brush each of them with some milk, add ½ teaspoon of granulated sugar and a pinch of ground cinnamon.
Take to a preheated oven at 180° C (350° F) and bake for 30 minutes.
Serve.