Last time it came out great, lots of lamb flavor. I was able to make a really good balsamic reduction sauce with the juices. Quantities were limited though. This is one reason to limit what you include in cooking the lamb, as it can impact the juice flavors and thus the sauce.
Minimal roasting: sprinkle salt, pepper and juice of lemon before putting in oven. Cook at high temp to braise in the beginning (475 convection for 30 min). Optionally add herb paste to top. Then reduce temp to 350 and cook until about 145F. Let cool for 30 min. It will continue to cook.
Herb paste: 1 cup parsley leaves, cup of dill sprigs, 3-4 green onions, couple stalks of celery, quarter cup of fresh marjoram, lemon zest from 1-2 lemons. Lightly chop in food processor.
Laura Vitale puts fresh rosemary and garlic cloves into slits. Squeezes and rubs half a lemon over surface. Small drizzle of olive oil, then salt and pepper. She makes a simple sauce with leftover juice by pouring out most (unneeded fat), adding white wine and fresh rosemary, and putting back in oven 350F for 15 min or so.