Tuna Rolls With Roasted Shallot?Wasabi Sauce

Name: Tuna Rolls With Roasted Shallot?Wasabi Sauce
Ingredients: Kosher salt; 4 large shallots; 2 teaspoons wasabi powder; 2 teaspoons hot water; 1 tablespoon fresh lemon juice; 1 tablespoon soy sauce; 1 tablespoon vegetable oil; 1/4 teaspoon Asian sesame oil; 1 pound sushi-grade tuna, finely diced; 1/3 cup mayonnaise (see Note); 2 teaspoons sambal oelek or other Asian chili sauce; 10 ounces baby spinach, rinsed; 1 tablespoon sesame seeds; 1 scallion, minced; 8 sheets of phyllo dough; 2 tablespoons unsalted butter, melted; Vegetable oil, for frying