Pat fish dry with paper towels and season with salt and pepper. Heat oil in 12-inch nonstick skillet over medium-high heat until shimmering. Cook fish until golden brown and registering 140 degrees, about 2 ½ minutes per side. Transfer fish to platter and tent loosely with foil until ready to put in your spring roll.
Set up rice paper-rolling station with all ingredients along with a shallow bowl with 1 inch of very warm water.
For each roll, slide a rice paper round in the warm water for 10 seconds to wet both sides, them place on a cutting board or dinner plate.
When rice paper is pliable, smear 1 teaspoon peanut sauce in the center of the lower third. Layer 10 cooked rice noodles, 1 Tablespoon cooked perch, 2 Tablespoons cabbage, 2 Tablespoons sweet potato, 4 carrot matchsticks, 4 bell pepper matchsticks, 1 teaspoon cilantro, and 4 - 6 fresh spinach leaves. Bring up the bottom edge to cover the filling and roll twice. Fold in the sides and finish rolling to seal.
Present rolls, whole or cut in half with remaining peanut saucefor spooning onto the rolls.