You need help from one of our Roland users to get down into the TD-20's menus and figure out what needs to be toggled to deal with MIDI input from a Zendrum vs. Roland pads and pedals...(Are you listening Drumhead 99?)
What I know is that MIDI notes can be "grouped" to cut one another off when struck. This requires developing your own version of Zendrumming technique that most closely simulates the effect of open/closed hi-hats or choking cymbals.
The more attention you pay to the detail of ALL the sounds you can get from one acoustic drum or cymbal, the more challenging this can be to get "right" with any electronic drum module. What a lot of us have done is assign multiple triggers different MIDI notes with similar sounds and just change the stereo panning and tuning just a little. From the drum throne perspective, this gives me the sound I hear acoustically of left and right hand sticking. I've always done this on every snare, tom, and cymbal sound I use in my "drumset". This also gives me the ability to send separate MIDI notes that will "play through" better than one MIDI note shared by multiple triggers playing the same exact sound. That's where the machine gun snare sound starts to be less obviously electronic and where you can fool the module into producing more nuance and detail than its normal factory presets will allow.
Zendrumdude (Jer) posted a while back about how to assign the Zendrum sustain button to act as a choke on an Alesis DMPro. That post has since been archived at the Zendrum Resource by Geo. It might give you the overview of what you need to get from your TD-20.
The parameters offered may be called by different names on the Roland, but I'd bet the functionality is the same.
As far as the drumset goes, you'll be gaining the ability to sound like a room full of drummers playing at the same time while taking up the same space as a guitarist or bass player. You'll also be the first guy out the door-not the last.
I have to simulate both of the Allman Brother's drummers on a couple of tunes with drum solos.
That's almost too easy.
The "trick" to Zendrumming is not sounding like a herd of elephants stampeding all the time (unless that's your REAL intention).
Just like with any drumming, the key is to relax and play good time and control the dynamics, first.
The finger rudiments and superchops will come with dedicated practice over time.
I still learn something every time I see another new Zendrummer's video.
We all do this SO differently from one another, there can't possibly be any rules laid down.
That's pretty cool...