Preheat oven to 400 degrees. Mix garlic, rosemary, salt, pepper, olive oil, mustard, and lemon juice in a small bowl. Reserve 1 tablespoon of mixture. Spread remainder over fat side of pork. Place pork fat side up on a wire rack in a roasting pan. Place pork in oven. Reduce heat to 325 degrees and cook uncovered 2 hours. Toss asparagus with 1 tablespoon reserved garlic mixture. Arrange asparagus around roast and cook uncovered 15 to 20 minutes. Serve immediately.