SiFive has E-series (aka "Freedom Everywhere") and U-series (aka "Freedom Unleashed") cores, both of which seem to be based on Rocket. And they do provide high-level designs for both on their GitHub, under a free license.

High-level designs of the SoC, not of those cores themselves is public for some platforms.

Based on whatever for the core doesn't matter, as the cores themselves in any case diverge quite a lot from Rocket.