Preheat your oven to 350℉. Spray a muffin tin with nonstick cooking spray. Set aside.
Wash the apples, cut them in half lengthwise, and remove the core.
Slice the apples thinly widthwise, keeping the open side of the apple down. Put the thinly sliced apples in a bowl and add the juice of half a lemon.
In a small bowl, combine the sugar and ground cinnamon. Sprinkle 1-2 teaspoons over the sliced apples and set the rest of the sugar-cinnamon mix aside.
Unfold the thawed sheet of puff pastry onto a lightly floured surface or a piece of parchment paper.
In a microwave-safe bowl, melt the butter. Using a pastry brush, cover one side of the puff pastry sheets with melted butter. Sprinkle with the remaining sugar and cinnamon mixture.
Using a pizza cutter or knife, begin at the short end of the puff pastry sheet and cut each puff pastry sheet into six equal strips.
Place apple slices, skin side up, along the long edge of the dough, overlapping slightly, until you get to the end of the pastry strip. Fold up the bottom part of the dough.
Gently roll up the apple and pastry into a rose shape and place it in the prepared. Repeat until all 12 roses are rolled up.
Place the muffin pan in a preheated oven for 25-30 minutes or until golden brown. Allow to cool for 10 minutes before serving. Sprinkle with powdered sugar.