Mix the oil, salt, cumin, oregano, black pepper, red pepper, garlic, lime juice and orange juice in a small bowl. Make slits in the pork with a paring knife and rub liberally all over with the oil mixture. Place the pork in a slow cooker and top with the remaining juices from the bowl. Cover and cook on low until tender, flipping once halfway through, about 6 hours.
Remove from the slow cooker and let cool slightly. Shred the pork into thick chunks with 2 forks. Set the pork aside and keep warm in the cooking liquid.
Slice the roll open and smear both sides with mustard. Layer on the Swiss, ham, pulled pork and pickles. Place the onions over half the sub and cut into portions. Or, start on opposing ends and race to the middle.