This is ALPHA1 of RoleAssign for Drupal 8, ported from 7.x-1.0.
It has all the functionality of the D7 version, including migration from D7 and D6.
RoleAssign for D8 has not received any real-world testing — we do not recommend installing it on a production site, but we encourage you to test it and provide feedback (both good and bad!) in the issues queue. See #2622542: RoleAssign for D8 for details.