Heat oil in frying pan over medium-high heat and sear all sides of roast.
Add layer of sliced sweet potatoes and carrots on bottom of slow cooker and place seared roast on top.
Add beef broth or water to slow cooker and pour balsamic vinegar over top and sides of roast.
Press minced garlic on top of roast. Add rosemary, bay leaves, thyme, pepper, and chili powder to the top and sides of roast. Add chopped onion on top and around the roast.
Cook on low for 6-7 hours or until interior temperature reaches at least 160 degrees Farenheit.