Place roast in slow cooker. Pour low sodium beef broth over top and cook on low for 6 hours.
During the last 30 minutes of cooking time, cook the sweet potatoes by placing them in a skillet with the onion and taco seasoning (reserve 1/2 teaspoon taco seasoning for the dipping sauce).
Pour water over all. Cover and cook for about 10 minutes over medium heat.
Add olive oil and cook for a few minutes longer or until potatoes are fork tender and start to brown.
In another bowl make the dipping sauce by mixing the sour cream, hot sauce, and 1/2 teaspoon taco seasoning until smooth and creamy. Set aside for dipping.
When beef is done cooking, shred with a fork.
Add beef to the potato mixture and stir together.
Spoon onto tortillas and garnish with chopped cilantro.