Rub pork with 3 tablespoons mustard, season with pepper and place in a 5- or 6-quart slow cooker. Add ham and pickles, including pickle juice. Cover and cook on low 6 hours or until tender, turning halfway through.
Shred pork with 2 forks. Sprinkle cheese over meat mixture; cover and cook until cheese melts, about 30 minutes.
When ready to serve, slice rolls and toast lightly in a toaster oven or broiler. Spread remaining mustard evenly over both sides. Using a slotted spoon, top rolls with meat mixture. Serve immediately.
