Using tip of knife, make long, shallow cuts in cross-hatch pattern on top side of skin, taking care not to cut through skin. Season skin with Adobo, transfer to zip-top bag and set aside. Transfer pork to large non-reactive container. Pour Mojo over pork to completely submerge; cover with plastic wrap. Refrigerate pork and reserved pork skin at least 4 hours, or up to 48 hours.
Heat oven to 425°F. Bring pork and skin to room temperature 30 minutes before cooking; discard marinade. Meanwhile, heat oil in medium skillet over medium-high heat. Add onions and garlic; cook, stirring occasionally, until onions are soft and translucent. Transfer cooked onion and garlic mixture, plátanos and breadcrumbs to bowl of food processor. Pulse until ingredients are well-combined and come together as smooth dough, about 30 1-second pulses; set aside.
Using paper towels, pat pork and skin dry. Place pork on work surface so that short side is closest to you. Season pork with Adobo. Spread plantain mixture evenly on pork, leaving 1” boarder all around. Starting with short side, roll pork, jellyroll-style to enclose plantain mixture, creating cylinder shape. Lay skin fatty side-down over pork. Using kitchen twine, firmly tie rolled pork in 1” intervals. Transfer pork, seam side-down to roasting pan. Pour 2 cups water into bottom of pan.
Roast pork 30 minutes. Rotate pan and reduce heat to 375°F. Roast, occasionally turning pan for even browning, until cooked through (temperature will register 160F on quick-read thermometer when inserted in center of pork, touching the stuffing ), about 3 hours, 15 minutes – 3½ hours, adding water in ½ cup measurements if pan becomes dry.
Transfer pork to cutting board. Remove and discard twine. Remove skin and cut into service pieces. Let pork rest 20-30 minutes. Meanwhile, drain fat from pan drippings. Slice pork and serve with pan juices and crunchy pork skin.