In a bowl mix together salt, pepper, chili powder, granulated garlic, cumin and oregano.
Rub mixture all over beef roast to completely coat.
In a large pan heat olive oil. Brown roast on all sides, about 5 minutes per side.
Place in slow cooker. Add onion and garlic. Pour in water and beef broth. Cover and cook for 8 hours.
Remove from slow cooker and shred.
Preheat oven to 350 degrees. Spray baking sheet with non-stick spray.
Heat 2 tablespoons canola oil in a small skillet over medium-high heat. Once hot, fry each tortilla one at a time until soft, about 30 seconds per side (you want them soft so that you can roll them). Add more oil if needed. Transfer to plate using a paper towel to separate each tortilla.
To assemble, spoon 2 tablespoons of meat mixture into tortilla and roll closed. Place on prepared baking sheet. Repeat until all are rolled.
Bake in oven for 15 -20 minutes or until ends start to brown. Remove and sprinkle cheese on top. Turn oven setting to broil and broil for 2-3 minutes or until cheese melts. Remove from oven.
Top with shredded lettuce and guacamole. Serve with salsa for dipping.