Preheat oven to 425°F and line a large rimmed sheet pan with parchment.
Whisk miso sauce as written.
In a bowl, toss chicken with half the sauce.
On the sheet pan, toss all veggies and cashews with remaining sauce plus neutral oil; spread in an even layer.
Arrange chicken pieces over and among veggies.
Roast 20–22 minutes, until chicken reaches 165°F and veggies are tender with browned edges.
Toss everything together on the pan; if you reserved a tablespoon or two of sauce, drizzle it on now and serve with rice and toppings.