Rotondo: should spawn zombies at you depending on your status. If you are in a vehicle, he spawns Boomers and tanks. If you have a high amount of health, he spawns hoards of zombie normal/slow at you. If you have low health, he spawns 1 zombie Hunter/fast at you every wave. Problem: This would take some serious stuff to make.
Kompressor: can freeze your player for a moment and fire a rocket at you. The way you avoid it is by avoiding the reticule (which should be a red 3D sphere that floats around and locks on to you) if you kill the reticule, then he just shoots rockets at you.
Ephialtes: should launch a "Fail bin" and try to trap you in it. If you get trapped in it, the only way out is using your weapon on its bottom, which will eventually break and you fall out. Oh, the Fail bin sometimes shoots a flame from inside, which hurts you, so you will want to get out.
Badspot: Should be like a 3D fight with bowser in the original Super Mario bros.

He throws Ban Hammers, which are a one hit kill. His secondary attack is verbal ownage, which is ranged and comes from his mouth.
*Whew* That's my view of the boss fights, feel free to criticize on it (HELPFUL criticism only, please)