As soon as word hit that Rockman Online might be cancelled, I immediately began hoarding whatever assets I could find. In my scramble, I stumbled upon the above footage of Studio Doma recording a track from the game. This piece sort of sounds like it went along with Online's planned pyramid stage. It's quite tranquil, don't you think? Hard to believe this one slipped right underneath our radar!
And then there's this piece by Seunghyuk Yang dubbed "Interface." I imagine this went along with the game's menu screens or something of that sort. It's very Matrix-y.
Also gone unnoticed, Studio Doma's Rockman Online portfolio. The page looks like it once hosted six soundtrack samples. UPDATE: Courtesy of Gauntlet101010 of The Mechanical Maniacs, here's a playlist of all six tracks. They're VERY short, but better than nothing: