Add the onion, potatoes, mushrooms, garlic, arrowroot starch, paprika, garlic powder, onion powder, Italian seasoning, black pepper, beef broth, thyme, and rosemary. Toss to combine.
1 onion, 1 ½ lbs baby potatoes, 8 oz mushrooms, 6 cloves garlic, 2 Tbsp arrowroot starch, 1 tsp paprika, 1 tsp garlic powder, 1 tsp onion powder, ½ tsp Italian seasoning, ½ tsp black pepper, 1 cup beef broth, 1 Tbsp fresh thyme, 1 Tbsp fresh rosemary