Preheat the oven to 400°
Prick the tenderloin all over with a fork. Mix oil, Worcestershire, smoked paprika, onion powder, garlic powder, salt, and pepper. Rub all over the pork. Bake on a rimmed sheet pan for 20-25 minutes, or until a meat thermometer registers about 150 degrees. It will be a little pink at the center. Allow the meat to cool and chill in the refrigerator for at least 30 minutes to an hour before slicing. You can also cover the pork and chill overnight if you like.
Lower the heat to 350° and clean the sheet pan. Combine the melted butter and dehydrated onion. Separate the rolls and brush the tops of the rolls with the butter mixture. Bake for 8 minutes.
While the rolls are in the oven, put the marmalade in a small microwave-safe bowl, and microwave for 20-30 seconds to loosen. Stir in mustard.
Slice the chilled tenderloin in ¼-inch slices. Serve the pork with the sliced rolls and orange mustard. Alternately, make sandwiches and store them in air-tight containers, or wrap individually.