Heat the olive oil in a skillet over medium-high heat. Brown the lamb cubes on all sides, then transfer them to the slow cooker.
Add the onion, carrots, and garlic to the slow cooker.
Pour the red wine and beef broth into the slow cooker.
Stir in the tomato paste, rosemary sprigs, bay leaf, salt, and black pepper.
Cover and cook on low for 8 hours until the lamb is fork-tender.
Remove the rosemary sprigs and bay leaf before serving.