There are no speed controllers (to my knowledge) that accommodate anything more than two channels. Mainly because any RC vehicle requiring speed control never usually needs more than two motive sources to make it move.

Looking at your intended setup, this would be the most common arrangement:

Ch.1 & Ch.2 - Drive. Either through two individual speed controllers (possibly linked by a mixer to give joystick-style control) or by a dual motor controller.
Ch.3 - Flipper. You would want a switch of some kind to control a solenoid (electric coil) which activates the valve and allows the flow of gas.
Ch.4 - Srimech/flip switch. A srimech that is not part of the flipper would probably take the form of a motor or linear actuator. In this case, another ESC would most likely be used. I can't remember the exact specifics of setting up a flip-switch (not too difficult though) but again, this would most likely require a switch of some kind.

The flipper probs wont self right, since I'm planning a funny shape for it, hence channel 4.
Flippers can take up a lot of weight at the best of times, so having to incorporate some form of self-righting mechanism into your robot alongside the flipper would take up valuable weight. Since your robot isn't built yet, I'd advise that you don't design such weaknesses into your robot. Alter the shape slighty so that the flipper will self-right the robot.
The first Drumroll had small wheels that didn't stick out the top. I knew this in the design stage but pressed ahead with the build anyway as I figured I could just stick some roll-hoops on it. But the roll hoops didn't do their job on several occasions which cost me the chance of a win. If I'd spent just ten minutes revising the design before construction began, the robot would have been invertible and it would have been able to avoid the problems of not self-righting in the middle of a fight.

EDIT: Jonny and Max beat me to it!