This dish is just as delicious if you trade the pasta for a cooked whole grain—think farro or barley.
Place a rack in center of oven; preheat to 375°F. Line a large baking sheet with foil; oil foil. Pulse scallions, cilantro, oil, garlic, vinegar, paprika, honey, salt, and pepper in a food processor to form a paste. Rub chicken all over with 2/3 paste; arrange in a single layer on baking sheet. Roast until golden and cooked through, about 25 minutes. Transfer to a cutting board; let rest for 5 minutes before slicing.
Bring a large pan of water to a boil; have ready a bowl of ice water. Blanch peas until just tender, about 1 miunte. Scoop out peas with a slotted spoon; transfer to ice water. Bring cooking water back to a boil. Cook pasta until just tender, 10 to 12 minutes or according to package directions. Drain pasta; immediately toss in a bowl with remaining scallion paste. Slice peas and add to bowl. Add radishes; stir to combine.
Divide pasta among 6 bowls. Top with chicken and serve.