Soak bean thread noodles in warm water for 5 minutes to soften. Drain and cut into short lengths.
Using a mortar and pestle, pound garlic, peppercorns, and coriander roots into a fine paste.
Heat vegetable oil in a pan over medium heat. Add the garlic paste and cook for about 1 minute.
Add ground pork and cook until just done.
Stir in noodles, carrot, cabbage, and fish sauce. Cook for about 3 minutes until vegetables soften. Adjust seasoning with more fish sauce if needed. Let the mixture cool completely.
Mix plain flour and water to form a thick paste for the spring roll glue.
Place a heaped tablespoon of filling onto a spring roll wrapper. Fold the wrapper like an envelope and roll tightly, sealing the edge with the flour paste. Repeat with the remaining wrappers and filling.
Preheat the air fryer to 390°F (200°C).
Spray the air fryer basket with cooking spray. Place the spring rolls in the basket in a single layer.
Spray the spring rolls lightly with cooking spray.
Air fry for 14 minutes, turning halfway through cooking (7 minutes per side), until golden and crisp.