Using kitchen string, tie the roast crosswise at 2-inch intervals. Brush all over with the chimichurri-drippings mixture. Brush the grill grate and coat with oil.
Grill the roast directly over the heat until browned all over, 8 to 10 minutes total.
Use tongs and a spatula to move the roast to the unheated area of the grill, and close the lid.
Shrimp Paella: A Spanish Delicacy 