Pre-heat oven to 400 degrees F
Grease muffin tins with butter generously, also butter around the top edge as rolls will puff over.
Roll out puff pastry sheets onto a non-stick surface (like parchment paper or floured counter).
Sprinkle with cinnamon sugar mixture generously (you will not use all the mixture, reserve in airtight container).
Scatter on the marshmallows and chocolate chips, leaving 1/4 inch of pastry free of anything at the far end.
Carefully roll up the puff pastry sheet (some chips and marshmallows may fall out).
When you get it all rolled up press slightly down to press the ingredients and pastry together. Do not smash it down, it should still keep its roll shape.
Cut roll in 4 pieces, I found a bread knife worked well.
Place each roll into muffin tin cavity. Gently press down on the roll to secure in muffin tin.
Place a small pat of butter on top of each roll.
Bake for 15-17 minutes, until golden brown on edges and tops.
Make buttercream:
Cream butter in mixer until light and fluffy.
Add powdered sugar in small amounts and blend well, repeat until all powdered sugar is used adding milk in between as needed.
If making Orange Buttercream, add the marmalade, zest and mix.
Set aside.
When rolls are done let cool 10 minutes.
Add scoop of buttercream to each roll.