The cooking time for a boneless leg of lamb depends on the desired doneness and the weight of the roast. Here are the general guidelines:

• For rare (125°F internal temperature): about 15 minutes per pound.
• For medium-rare (130-135°F): about 20 minutes per pound.
• For medium (135-140°F): about 25 minutes per pound.
• For well-done (155-160°F): about 30 minutes per pound.

These times are based on roasting at around 325°F to 350°F. For example, a 4-pound boneless leg of lamb cooked medium-rare would take approximately 80 minutes (20 minutes × 4 pounds)

. Additional tips:

• Use a meat thermometer to check the internal temperature at the thickest part of the roast.
• Remove the lamb from the oven 5-10°F below the target temperature to allow for carry-over cooking while resting.
• Let the roast rest for 10-15 minutes before slicing to retain juices and finish cooking

• Cooking times may vary slightly depending on oven temperature and whether the roast is tied or rolled.

In summary, plan on about 20 minutes per pound for a medium-rare boneless leg of lamb roast at 325-350°F, adjusting based on your preferred doneness and always verifying with a thermometer for best results.