Place flour in a shallow dish. Combine egg whites and water in a small bowl. Place breadcrumbs in another shallow dish. Dredge oysters in flour. Dip oysters in egg white mixture, and dredge in breadcrumbs.
Heat the oil in a large nonstick skillet over medium heat. Add breaded oysters to skillet; sauté 5 minutes on each side or until golden brown. Remove from heat.
Combine lettuce, tartar sauce, and juice in a medium bowl. Arrange 1 1/2 ounces ham and 2 tomato slices over bottom half of each roll; top each with 3 oysters, 1/2 cup lettuce mixture, and top halves of rolls. Garnish with lemon wedges, if desired. Serve immediately.