Just the module and some triggers is all you need unless you want and can afford the full kit. It doesnt even have to be a Roland either and many kits components can be mixed and matched, just make sure you like the way the module sounds and that it has enough inputs for as many triggers as you plan to use. The concept of converting your acoustic kit to be used with a second hand mid level module is more about saving money really. If you can afford an entire E kit or can find the one you like used instead, by all means get it because it will already be set up to work ideally with its own module and may offer additional features like stereo pads or mesh heads. This doesnt mean you cant still modify your own kit to do the same thing but the task will get bigger and more expensive the more you want to do with it.
MY KIT: I first picked up a used Yamaha DTX kit for cheap that I used by itself for a while, then later added a small acoustic kit with the Red Shot triggers. I then got mesh heads to play in total silence and will eventually get rid of the Red Shots in favor of permanently intigrated home made triggers with stereo functionality. I'll probably upgrade the module at some point too. This was all a lot more work than just getting a new Roland kit from the get go, but all I could afford to do was build the kit in stages and its actually very nice now.
