Here's an official/final list of the robots appearing in the TRANSFORMERS movie, per the recently announced web chat with writers Alex Kurtzman and Bob Orci.
AUTOBOTS: Optimus Prime. Bumblebee ("The same G1 character we always knew and loved...He's the scout, the one that comes ahead of the Autobots"). Jazz. Ratchet (medical officer/science officer - new form, not an ambulance). Ironhide ("He's the muscle - a tough soldier...The first one to jump into battle" ).
DECEPTICONS: Megatron (has a Social Darwinist view of humanity - survival of the fittest). Starscream. Brawl ("an extremely pissed off Decepticon. Always ready to jump into a fight, even when the fight isn't worth it.") Bonecrusher. Barricade. Scorponok. Frenzy (an infiltrator). Blackout (sends an EMP-style blast to take out electronics, detection devices, etc. in advance of Decepticon attack).
Also announced: a forthcoming contest in which fans will be able to write a line of dialogue for Optimus Prime that'll be used in the movie. Details on this when they're available...