Wesley: He is the principal character and you start with him. Wesley is an Engineer with blue hair. Unlike the other heroes (except Tower and Juggernauts with astronaut helmet), Wesley is the only one wearing special glasses without showing his eyes.
There are more people to recruit, it's only that those characters are non-unique.
The Female Heroes (except for Evelynn) first appeared on Strike Force Heroes Extraction
The Male Heroes first appeared on Strike Force Heroes 2
Dex is a Mercenary from United States. He was the one who killed West in Strike Force Heroes 2 and joined GlobeX all for money! However, the GlobeX Leader stomped Dex and cloned him. Fortunately Dex is back on the heroes side. Dex is recruited if you beat Rocket Race 4.0 on Insane
Rusty is a Knight. He's from A Knight's Quest. To recruit Rusty, you must play version 20.8 of Strike Force Heroes 3. If its the first time playing, you will have to beat level 3 once your starting the game (unless you already did). Then below will be an advertisement about A Knight's Quest, next to it will say New Knight Hero, click on it and it will say Unique Hero: Knight. Press OK and recruit the new hero and it should give you Rusty.