In a blender or food processor, combine the diced tomatoes, chili pepper, garlic clove, paprika, cumin, salt, pepper, lime juice, and oil. Blend until smooth to create the marinade.
Cut the whole chicken along the breast and open it in a pan. Spread the marinade on both sides of the chicken, making sure to cover it evenly. Place the chicken in the refrigerator and let it marinate for at least 1 hour, allowing the flavors to permeate the meat.
Preheat the oven to 180°C (350°F).
Transfer the marinated chicken to a roasting pan and place it in the preheated oven. Roast the chicken for approximately 1 hour and 15 minutes, or until the internal temperature reaches 165°C (329°F) and the skin is crispy and golden brown.
While the chicken is roasting, wash the potatoes and place them in a separate baking tray. Put the tray with the potatoes in the oven alongside the chicken. Roast the potatoes for about 40-50 minutes, or until they are tender and cooked through.
Once the potatoes are done, remove them from the oven and let them cool slightly. Cut the potatoes in half and place them in a serving dish. Add butter, chopped oregano or parsley, salt, and pepper to taste.
Remove the roasted chicken from the oven and let it rest for a few minutes before carving. Serve the Whole Roasted Mexican Chicken with the buttered parsley potatoes on the side, cream, and optionally tomatillos salsa.
Enjoy!