In a bowl, mix olive oil, minced garlic, chopped rosemary, salt, black pepper, and lemon juice. Coat the lamb shoulder in this marinade and let it sit for at least 2 hours, preferably overnight in the refrigerator.

Preheat the Oven

Preheat your oven to 350°F (175°C).

Sear the Lamb

In a large skillet over medium-high heat, sear the marinated lamb shoulder on all sides until browned, about 5 minutes per side.

Add Vegetables

Transfer the seared lamb to a roasting pan and add chopped carrots, quartered potatoes, and chopped onion around it.

Pour Wine

Pour the red wine over the lamb and vegetables.

Roast

Cover the roasting pan with foil and roast in the preheated oven for 2 to 2.5 hours, or until the lamb is tender and the internal temperature reaches 145°F (63°C).

Rest and Serve

Remove the lamb from the oven and let it rest for 15 minutes before slicing. Serve with the roasted vegetables.