Vietnamese Turmeric Fish Summer Rolls

Name: Vietnamese Turmeric Fish Summer Rolls
Ingredients: 4 Persian cucumbers; 1 pineapple; 1 2 piece ginger; 4–6 garlic cloves; 1 tsp. ground turmeric; 4 Tbsp. fish sauce, divided; ½ tsp. crushed red pepper flakes, plus more; Kosher salt; 1 lb. white fish fillets (such as red snapper, hake, halibut, or tilapia), preferably skin-on; 1 Tbsp. sugar; 1 lime; 1 Tbsp. vegetable oil; 12 rice paper rounds; Tender lettuce (such as green leaf or Bibb) and tender herbs (such as cilantro, dill, and/or Thai basil); for serving