That's a very small piece of lamb so I would sear it first since it won't cook long enough to give it a good carmelized crust. Use your meat thermometer with the degree of doneless Uncle Bob posted. Lamb should NEVER be cooked well done. Be sure to let it rest for about 15 minutes. I love lamb but I usually do a 4 or 5 lb. leg of lamb roast.
Welcome to DC KatieHolmesxxxx!! I find this thread rather amusing as in Australia we had an advertising campaign a few years ago for lamb where the daughter gives up a dinner date with Tom Cruise to stay at home and have her mum's lamb roast instead!! It was a catch cry hear for years after the ads had stopped!
The weight could be in kilos not pounds as nearly 2kgs isn't that small for a lamb roast.