In 12-inch skillet, heat oil over medium-high heat. Add pork roast pieces. Cook 6 to 8 minutes, turning occasionally, until well browned on all sides.
In 3 1/2- to 4-quart slow cooker, place pork. Add water to skillet; cook over medium heat 2 to 3 minutes, scraping up browned bits. Pour over pork. Top pork with taco seasoning mix and chiles.
Cover and cook on Low heat setting 7 to 8 hours.
Remove pork from cooker to cutting board. Pull pork into bite-size chunks, using 2 forks. Return pork to juices in cooker.
Place cheese and salsa in separate serving bowls. On serving platter, arrange cheese, salsa, tomato, cilantro and lime pieces. Warm tortillas as directed on package. Spoon pork onto tortillas, using slotted spoon; top with cheese, tomato, cilantro and salsa. Squeeze lime juice over fillings. Fold tortillas in half over filling.