Unlike grilling, roasting does not involve direct heating, and is hence a much slower cooking process. Typically done using an oven, the hot air in the oven ensures an even heating and cooking on all sides of the meat.
Ensure that your meat has thawed to room temperature, and let your oven preheat for minimally 20 minutes before you begin. For added juiciness, coat your meat with some butter or oil (not too much), before you add your seasonings. Once you are satisfied, put it on your roasting pan and into the oven. Check that your temperature and time settings are correct, and leave your oven to do its job!