The voicing wasn't too bad. You need to work on a consistent volume.
Also, you could use a greater range of sound effects, e.g. when the robot hit the ground you could've made some exploding sound or something.
Background music would've been good, I find that it helps set the mood.
You used motion tween alot. Tweening is good if used properly. You did have some pretty good effects that made the robots look almost 3D, but I also saw some very bad points. For example, when the door opened, the robot went almost straight through the door (you can avoid this by using masks or simply not drawing the parts that are behind the door) and his feet didnt move AT ALL when moving closer towards the screen.
In addition, when your robot talked, what you did was draw the mouth as a circle but made it move randomly (or so that's what I think you did).
You could've either used actual lipsyncing (there's plenty of good tutorials for that here on ng)
OR even better (and easier): you could've just made the robot's mouths light on and off or move in a more machine-like way (such as open/close/open/close...)
One other thing, the first minute you had the three robots just sitting there, the same scene throughout. THIS IS VERY BAD. If you want people to keep watching, you should at least change the view every so often.
Overall a good attempt, the best part I liked in your flash is the part where the middle robot started drinking the oil. That scene, in my opinion, had the best animating. Also, the jet pack scene with the screaming showed me your true knowledge in animating, as, a beginner would not know of moving the buildings (instead of the the robot with jet pack) to create a sense of movement.
Keep at it.