Combine bell pepper, mango, carrot, green onions, and cilantro in a bowl. Toss until vegetables are evenly distributed.
Stir cashew butter, sesame oil, ginger, garlic, and Thai chiles together in a bowl until dressing is well mixed.
Fill a large bowl with boiling water. Dip 1 rice paper at a time into the water until soft, 2 to 5 seconds.
Lay 2 rice papers together, 1 on top of the other, on a flat work surface. Spread dressing over the middle and layer vegetable mixture on top.
Tuck in the sides of the rice paper and roll upwards, gently pushing down the vegetable mixture to tighten the spring roll. Repeat with the remaining rice papers. Let sit for 2 to 5 minutes. Slice on the diagonal and serve.