Prepare the grill with charcoal using the two-zone method, targeting 400 - 425 degrees Fahrenheit over the direct heat.
Grill one side the seasoned pork over direct heat for up to 5 minutes or until you see a nice char on the outside. Flip and grill the other side over direct heat for additional 4 - 5 minutes until you see good color.
Move the grilled pork loin to the indirect side of the grill and insert two remote meat thermometer probes into the thickest part of the roast and close the lid. Continue grilling over indirect heat until the internal temperature of the roast reaches 125 degrees F, using the probes or an instant read thermometer. This can take up to 30 minutes, so plan up to an hour of total grilling time for a full roast.
At 125 degrees, glaze the roast one time and then continue grilling over indirect heat. The glaze will caramelize (or tack up) while the pork loin continues to cook. Continue grilling over indirect heat an additional 20 minutes or the internal temperature reaches 140 degrees F. Remove the pork from the grill.
Brush the glaze on the roast again and let rest 10 - 15 minutes to allow carryover cooking occur. The roast will rise in temperature to 145 degrees F (or medium rare) while it rests and the additional glaze will thicken.
Slice the roast and serve with your favorite sides. Use any remaining glaze with the meal.