Rookie is currently unnamed, and the term "Rookie" is actually referring to his call sign given by the squadron. Rookie was originally this overconfident, "I can handle anything" type character in Trooper Down 2, and to some extent he still is for part of this game. Rookie is Talon's closest wingman, as well as his closest friend. Rookie was new to flying and eager to see some action, and while getting stuck in an alien system wasn't really what he had in mind, he didn't complain. 

Rookie's personality seemingly didn't change one bit, despite the games being 793 days apart, however his character goes through a bit of a change as he, in some way, matures a little. Commander Talon explains why he feels so incompetent, and after learning that the person he looked up to was unsure of himself, it was a slight eye opener for Rookie

Halfway through the mission, when everything turns south very quickly Rookie goes from enthusiastic and overconfident to dead silence as he is in a state of shock for pretty much the rest of the game

If you plan on voicing this character, he'll probably be the most "fun" so to speak. As mentioned, he has a cocky, overconfident tone of voice. He wont have as many voice lines, but he will possibly be in a sequel and a prequel game.