This is my first design on Tinkercad, I'm kind of surprised no one has uploaded any roller chain (that I could find, anyway). It is #40 chain, also known as 40RC or 40-1 or 1/2" industrial chain, for use with #40 chain sprockets. I'm not sure how well this will print, though I will certainly try when I get my Rigidbot in October. I think it would need to be printed twice to get enough to test.
Each copy of this print provides 2 chain links, a roller link and a connecting link. It also has the snap to secure the connecting link. I'm quite sure if you tried to put any real power through a plastic 3D printed version this chain it would disintegrate, but it could be used in low speed, low power applications. Assuming I got all the dimensions right.
This thing was made with Tinkercad. Edit it online https://tinkercad.com/things/6CgAxWCReCk

*** Update 10-27-14 - Finally had a chance to make this. I had to modify a couple of things to make this usable. I recommend printing this on a raft or the pins start to come loose.

**** Update 5.8.19 - Updated cover photo to show the difference from the links I printed with my RigidBot and those I just printed from my SLA printer, SparkMaker. Also uploaded a new .stl, fixed for SLA printers and with slightly longer pins that work better in general.