Heat oven to 400°F. Line cookie sheet with foil.
In 10-inch skillet, heat oil over high heat. Sprinkle taco seasoning mix over flank steak, pressing to coat. Brown steak in oil on both sides. Place steak on cookie sheet. Roast until meat thermometer inserted in center of steak reads 135°F. Remove from oven, and let rest 10 minutes.
Meanwhile, in large bowl, mix salsa ingredients. Refrigerate until ready to serve.
Cut steak into thin slices. Place 2 or 3 slices steak on each tortilla. Top with salsa. Roll up tortillas.