Place the beef chunks, sliced onion, and minced garlic into the slow cooker.
Pour the balsamic vinegar and beef broth over the beef. Add the rosemary, thyme, salt, and pepper. Stir gently to combine.
Cover and cook on low for 8 hours until the beef is very tender.
About 45 minutes before the beef is done, preheat the oven to 400 degrees.
In a large bowl, toss the carrots, parsnips, and potatoes with the olive oil, plus a pinch of salt and pepper. Spread them in a single layer on a baking sheet.
Roast the vegetables for 35 to 40 minutes, stirring once, until they are tender and edges are browned.
Spoon the beef and some of the cooking liquid into bowls. Add a portion of the roasted vegetables on the side and sprinkle with fresh parsley.