Place a large nonstick skillet over medium- high heat until hot. Add steak; sauté until browned. Drain well. Place steak in a medium bowl; set aside. Wipe skillet clean with paper towels.
Place skillet over medium-high heat until hot. Coat mushrooms, shallots, and garlic with cooking spray; add to skillet. Cook, stirring constantly, until tender. Add wine, thyme, and pepper; cook 8 minutes or until most of liquid evaporates. Remove from heat; stir in gravy. Add mixture to steak in bowl; stir well, and set aside. Wipe skillet clean with paper towels.
Place skillet over medium-high heat until hot. Coat potatoes with cooking spray. Add potatoes to skillet, spreading to an even layer; add salt. Cook 5 minutes (do not stir). Turn potatoes over, and cook an additional 5 minutes (do not stir). Add potatoes to steak mixture in bowl, and stir well.
Warm tortillas according to package directions. Spoon steak mixture evenly down the center of each tortilla, and top with lettuce; roll up. Wrap bottom of rolled sandwiches in wax paper or parchment paper to secure.