Preheat oven to 375 degrees F.
In a small mixing bowl, stir together salt, lemon pepper, dried basil and poultry seasoning. Rub olive oil all over the hens and season each with the salt mixture. Place the hens on a baking sheet pan with plenty of space between them. You may need to use 2 pans. Loosely stuff the cavities of each hen with some green bell pepper, celery and onion. Roast the hens in the preheated oven for about 1 hour or until an instant-read thermometer inserted into the thickest part of the thigh registers 165 degrees F and the juices run clear. Remove the hens from the oven, loosely tent with foil and let rest 10 minutes before carving or serving.
Line the baking sheet pan with foil under the wire rack for an easy clean-up. The veggies and herbs stuffed in the cavities of the hens will impart flavor to the meat as it cooks. Be sure not to crowd the hens on the baking sheets or else the skin won't crisp up properly and they will take much longer to cook.