Courtesy of our friend VixyNyan, you can download the complete soundtrack from good 'ol Rockman Perfect Memories here. Each piece is individually ID tagged, too. And fun fact: the soundtrack was composed by Hitoshi Sakimoto. He's best known for his work on Final Fantasy Tactics, Final Fantasy XII, Gunstar Heroes and Vagrant Story!
If you're just catching up, a cancelled and unreleased Game Boy port of RockBoard surfaced early this month during the latest round of "Nintendo Gigaleaks." The game is a near 1:1 port of its Famicom sibling -- multiplayer included. The port was developed between 1993-1994 by defunct Japanese developer Dual.
Based on initial findings, Game Boy RockBoard made it very far in development. In fact, it was cancelled sometime after getting into Lot Check. In other words, a commercial release was within reach. We do not know why it was cancelled, though. Chalk this one up to the many Mega Man mysteries.
Many thanks to VixyNyan and nensondubois_!