Light the oven's back burner, setting it to two notches above low. Leave the bottom burner off. This will result in an oven temperature of about 425°F.
While the oven is preheating, add the olive oil, miso, maple syrup, butter, mirin and vinegar to a small saucepan over medium0low heat on the cooktop. Whisk the ingredients together and bring them to a simmer. Then, add the remaining glaze ingredients to the liquid and whisk until well incorporated. Remove the glaze from heat, and set aside.
Add the vegetables (except the green onions) to a large mixing bowl. Pour the warm glaze over top of the vegetables, and toss to coat them.
Transfer the glazed vegetables to a parchment paper lined baking sheet, evenly spreading them out in a single layer. Season the vegetables with salt and pepper and place them into the preheated oven. Rotate the baking sheet 180° every ten minutes to ensure even browning. Roast the vegetables for 35-40 minutes, or until fork tender.
Remove the vegetables, garnish with green onions and serve hot.