Add potatoes and carrots to the bottom of a large, 6 quart slow cooker. Top with arm roast. Mix together garlic powder, onion powder, salt, oregano, rosemary and black pepper and sprinkle on top.
Pour beef broth around the roast. Cover and cook on low for 8 hours or high for 4 hours (low recommended for tenderness). When cooking is complete, remove roast and use a slotted spoon to remove vegetables.
Ideally shred the meat, keep covered and make gravy with the drippings. To make gravy - pour drippings into a pot on stove over medium high heat. Whisk 1 tbsp cornstarch with a bit of your broth until smooth, pour that in when bubbling. Stir to smooth and as thick as you'd like. If not thick enough repeat with 1 more tbsp cornstarch. Serve on top of shredded or sliced beef.