Preheat the oven to 425°F (218°C) and position the rack in the middle of the oven.
Halve the potatoes and place them in a bowl; toss with 2 tablespoons of olive oil and a generous pinch of salt and pepper.
Spatchcock the chicken by placing it breast-side down on a large rimmed baking sheet and cutting out the backbone with kitchen shears on both sides; discard or save the backbone.
Open the chicken flat, flip breast-side up, and press firmly on the breastbone to flatten the bird further.
Rub the remaining 1 tablespoon olive oil over the chicken skin, then season the chicken with garlic powder, smoked paprika, salt, and pepper.
Arrange the seasoned potatoes around the chicken on the baking sheet; sprinkle the fresh poultry herb mix (remove rosemary/thyme from stems if desired) evenly over the chicken and potatoes, then toss the potatoes to coat.
Roast in the preheated oven for 45–55 minutes (about 50 minutes for a ~3 lb chicken) until a thermometer inserted into the thickest part of the breast reads 165°F (74°C). If desired, broil for a few minutes to crisp the skin—watch carefully.
Let the chicken rest for a few minutes, carve, garnish with chopped parsley if using, and serve with the roasted potatoes.