Heat olive oil in a heavy saucepan over medium heat. Sprinkle salt and pepper over lamb cubes. Add lamb to hot oil and cook for five to seven minutes to brown. Transfer lamb to a plate and set aside. Add pancetta, cook for three to four minutes, then add shallot, celery, carrot, and garlic to the hot saucepan. Add red wine and red wine vinegar to deglaze, scraping the brown bits from the bottom of the saucepan. Reduce by half. Add rosemary, thyme, bay leaves, ground black pepper, juniper berries, and cans of whole plum tomatoes with juice, tomato paste, and stock. Lower heat and cover partially. Simmer for two hours or until liquid has evaporated by half and lamb is tender and falling apart. Season with salt and ground black pepper.
Serve ragu over pici pasta and top with Pecorino Romano.