Not much is known about Ratbat. Besides being under the control of Soundwave, his personality and abilities are mostly unknown. He can dodge enemy fire a lot better than the rest of Soundwave's forces, but so far that appears to be all he can do.
Ratbat was a part of Soundwave's forces that were sent out when Soundwave was investigating Ravage's return. Not only did Ratbat get less scenes than Beastbox, his scenes only involved flying and avoiding enemy fire. He must have retreated along with Soundwave.