Star Wars Zero Company splits its 12 specializations into two very different groups. Eight are standard: Assault, Gunslinger, Heavy, Medic, Scoundrel, Scout, Sharpshooter, and Soldier. Any custom recruit can train in them, and you can swap a standard specialization at the Den's Personnel facility whenever a mission calls for a different role.
The other four are exotic, and you do not pick them from a menu: the Jedi Padawan (Tel-Rea Vokoss), the Mandalorian Warrior (Cly Kullervo), the Astromech built in the Droid Bay, and a fourth class that is confirmed but not yet revealed. Exotic classes are tied to a character or a facility and cannot be reassigned, so they shape your fireteam for the rest of the campaign.
This page holds the tier list, a dossier for each specialization, and the dual-class loadouts that perform best on the 1.0 build. If you only want the roster, the short version lives in the all classes list.