How to Make It
In a small bowl, whisk the chile powder with the coriander, onion powder, sugar and chopped oregano. Set the turkey breast skin side down on a work surface. Drizzle with 1 tablespoon of the olive oil and season generously with salt and pepper, then rub with half of the spice mixture. Fold in the sides and tie up the turkey breast with twine to make a neat roast. Season the outside of the turkey breast with salt and pepper, then rub with the remaining spice mix. Drizzle with 1 tablespoon of the olive oil and let stand at room temperature for 1 hour.
Preheat the oven to 425°. On a large rimmed baking sheet, toss the potatoes, poblanos, onions and oregano sprigs with the remaining 1/4 cup of olive oil. Season the vegetables with salt and pepper and spread in an even layer. Set the turkey breast skin side up on the vegetables. Roast for about 1 hour, until an instant-read thermometer inserted in the thickest part of the turkey registers 155°; tent with foil if it browns too quickly. Transfer the turkey breast to a carving board and let stand for 20 minutes. Untie the roast and thinly slice crosswise. Serve with the roasted vegetables.