Prepare medium-hot banked fire in kettle-style grill. Season pork roast with salt and pepper. Grill over indirect heat, not directly over fire, in covered grill for 1 1/2 hours (about 20 minutes per pound).
Meanwhile, stir together barbecue sauce, jelly and chili powder. The last 30 minutes, start basting with sauce mixture every 5-10 minutes until internal temperature on a thermometer reads 150 degrees F. Remove roast from heat; let rest until temperature reaches 160 degrees F, about 10 minutes before slicing to serve.
Serves 8-12