Rinse chicken with water, inside and out, then pat dry with paper towels.
Rub the chicken inside and out with salt, white pepper, and bouillon powder, and set aside.
In a small pan set over medium low heat, combine oil or butter, minced garlic, herbs, paprika, onion, and cayenne pepper. Add enough so there is plenty for basting.
Stir for 30 seconds to a minute. Let this mixture sit for a little bit, about 5 minutes.
Generously rub the chicken with the spice combination, then refrigerate until ready to cook.
Preheat the oven to 375℉/190℃.
Add onions to the roasting pan or cast-iron skillet, then put in the chicken, breast-side up. Tie the legs of the chicken together with kitchen twine to help hold its shape. Toss the potatoes and carrots around the chicken. If desired, sprinkle with a tablespoon or more of onion powder.
Roast in the oven at 375℉/190℃ for about 1 hour and 15 minutes, or until meat thermometer inserted into thickest part reaches about 165-170℉/74-77℃. Brush the chicken and veggies with the Cajun marinade every 30 minutes.
Remove from oven; let the chicken stand 10 minutes before carving so the juices settle back into the meat. Serve with the roasted potatoes and a side salad.