Heat shortening on medium heat (it should be about 1" deep, so you may have to adjust the amount depending what size pan you use).
Add plantain pieces and fry until golden on all sides.
Drain on paper towel lined plate.
Using a tortilla press, smash the plantains between two pieces of parchment paper until about 1/4" thick. Try to keep them uniform. (You can use a rolling pin if you don't have a tortilla press).
Fry smashed plantains until golden on both sides. You will need to work in batches for this.
Drain again on paper towel lined plate.
Place whatever you'd like between two patacones and enjoy your roll!