Combine the first 8 ingredients in a bowl. Preheat the oven to 425 degrees F. Remove the roast (if wrapped in one) from its netted bag. Unfold the meat and sit flat on a work surface. Press on and place the spinach mixture in a row down the centre of one side of the meat. Fold the meat back into its original roast shape and tie with string. Set in a small roasting pan, brush with olive oil, and season with salt and pepper.
Roast 20 minutes, and then reduce heat to 325 degrees F. Cook lamb to the desired doneness, checking its progress with a meat thermometer. 70 minutes more cooking time should yield a medium, to medium rare roast. Set the lamb on a plate, tent with foil and rest 10 minutes before thinly slicing and serving.
Note: If you wish serve jus with the lamb, see “Options” below.
Note:The best way to gauge lamb doneness is to insert an instant-read meat thermometer into the centre of the thickest part of the roast. A rare roast will be done at 125 degrees F; a medium-rare roast at 125 degrees F to 130 degrees F; a medium roast will be ready 140 degrees F; and a well done roast will be ready at 150 degrees F. Remember that the meat will continue to cook when allowed to rest before slicing.