Prepare the pork: Mix the olive oil, 1 tablespoon salt, 1 teaspoon pepper, the cumin, oregano, red pepper flakes, garlic, lime juice and orange juice in a small bowl. Make slits all over the pork with a paring knife and rub with the oil mixture. Transfer the pork to a 6- to 7-quart slow cooker and top with any juices from the bowl. Cover and cook on low until tender, 8 hours.
Transfer the pork to a bowl and let cool slightly. Shred into thick chunks with 2 forks, then return to the slow cooker and keep warm in the cooking liquid.
Assemble the sandwiches: Slice the roll or rolls in half lengthwise and smear both sides with mustard. Layer on the ham, cheese, pulled pork, pickles and onion and cut into portions. Or, start on opposing ends and race to the middle!