Cut tomatoes in half. Whisk together ¼ cup tahini, 1 cup plain low-fat Greek yogurt, 1 tbsp. minced garlic, 3 tbsp. fresh lemon juice, and 1 tsp. kosher salt. Top each of 4 pieces warmed naan bread with 1½ cups baby spinach, a few pieces eggplant, 4 tomato pieces, and a spoonful of the yogurt mixture. Roll to eat.