Place the ground turkey in the bottom of the slow cooker. Break it up slightly with a spoon so it cooks evenly.
Add the diced sweet potatoes and frozen mixed vegetables on top of the turkey.
Pour the turkey broth and tomato sauce over the other ingredients.
Sprinkle the onion powder, dried rosemary, salt, and black pepper across the top.
Stir everything together until the ingredients are well combined.
Cover the slow cooker and cook on low for 6 to 8 hours, until the sweet potatoes are soft and the turkey is fully cooked.