Cook pork tenderloin according to the package's oven directions. Cut each roll in half and top with mustard, cheese, ham, and sliced pickles. Removed cooked pork from oven and let it rest for 5 minutes. Cut pork into 1/2" slices. Add the pork to the sandwiches. Add butter to hot griddle or grill pan. Place sandwiches onto griddle and cover with tin foil. Allow sandwiches to cook for 3 minutes, then press each sandwich down onto the griddle. Flip sandwiches over, cook for 3 more minutes or until roll is crisp and cheese is melted.