Heat the olive oil in a large skillet over medium-high heat. Add the beef cubes and brown them on all sides for about 5 minutes. Sprinkle the flour over the beef and stir to coat.
Transfer the beef to the slow cooker. Add the mushrooms, onion, carrots, potatoes, garlic, tomato paste, salt, and pepper.
Pour in the red wine and beef broth. Stir everything to combine and nestle the rosemary sprigs on top.
Cover and cook on low for 8 hours until the beef is fork-tender and the vegetables are soft.
Remove the rosemary sprigs before serving. Taste and adjust salt or pepper if needed.