In a bowl, mix the adobo seasoning, crushed red pepper, chili powder, celery salt, and black pepper. Rub the mixture evenly over all sides of the roast.
Arrange the uncooked bacon strips horizontally on a flat surface, and top with 3 green onions. Place the roast on top of the bacon and green onions. Place 3 green onions on top of the roast. Carefully fold over roast, wrapping with the bacon strips and green onions, and secure with kitchen twine.
Place a drip pan inside the grill, and lightly oil grill grate. Position the roast on the grill grate over the drip pan, and top with remaining green onions. Cover, and cook using indirect heat for 4 hours, to a minimum internal temperature of 145 degrees F (63 degrees C).