Adjust an oven rack to the lowest position and heat the oven to 250 degrees. Pat the lamb dry with paper towels and season with salt and pepper.
Heat the oil in a large Dutch oven over medium-high heat until just smoking. Brown the lamb well on all sides, 7 to 10 minutes, reducing the heat if the pot begins to scorch. Transfer the lamb to a large plate.
Pour off all of the fat from the pot. Add the garlic, olives, lemon zest, coriander seeds, cinnamon stick, and cumin seeds and nestle the lamb, with any accumulated juices, into the pot. Place a large sheet of foil over the and press to seal, then cover tightly with the lid. Transfer the pot to the oven and cook until the very center of the lamb registers 125 degrees on an instant-read thermometer (for medium-rare), 45 to 60 minutes.
Remove the pot from the oven. Transfer the lamb to a cutting board, tent with foil, and let rest for 20 minutes. Remove the rosemary from the jus in the pot, then cover to keep the jus warm.
Remove the twine, slice the lamb into 1/4-inch-thick slices against the grain, and transfer to a serving platter. Spoon the jus over the lamb and serve.