Soak the cedar plank in water for at least 1 hour.
In a large sauté pan combine the pineapple, sugar, vinegar, lime juice, jalapeño, cumin, salt, and pepper. Bring to a boil, and cook over medium-high heat for 7 to 10 minutes. If there is still a lot of liquid in the bottom of the pan, remove the pineapple with a slotted spoon and transfer it to a serving bowl. Continue to cook the remaining liquid in the pan over high heat for another 5 minutes, or until the liquid has reduced and thickened. Pour the liquid over the pineapple. Add the scallions and basil, and adjust the seasoning with salt. Mix well.
In a small bowl combine the rub ingredients. Season the rub evenly onto all surfaces of the roast. Allow to stand at room temperature for 15 to 30 minutes before grilling.
Prepare the grill for direct cooking over medium heat (350° to 450°F).
Place the roast on the soaked cedar plank. Brush the cooking grates clean. Grill over direct medium heat, with the lid closed, until the internal temperature reaches 155°F, about 1 hour. Carefully remove the roast and plank from the grill and let rest for 3 to 5 minutes before slicing. Serve warm with the salsa.