Remove chicken from packaging, discard giblets, pat very dry inside and out, and optionally truss by tying legs together and tucking wings under.
In a small bowl, whisk together olive oil, kosher salt, black pepper, garlic powder, onion powder, smoked paprika (or regular paprika), and dried thyme or dried rosemary.
Place the chicken breast-side up on a rack in a roasting pan; rub the seasoned oil mixture all over the chicken, reaching under the wings and into all crevices.
Stuff the chicken cavity with half a lemon, half a medium onion, and the smashed garlic cloves.
Preheat oven to 425°F (220°C).
Roast the chicken at 425°F for 20–25 minutes to crisp the skin.
Reduce oven temperature to 375°F (190°C) and continue roasting for 50–70 minutes, until an instant-read thermometer inserted into the thickest part of the thigh registers 165°F (74°C).
Transfer chicken to a cutting board, tent loosely with foil, and let rest 10–15 minutes.
Carve the chicken and serve with your choice of sides.