While the Roadmaps is in BETA, user management has limitations.
Here's the list of what users can do:
Workspace members and admins
can access the Roadmaps
can open all existing roadmaps
can create a new roadmap or delete existing roadmaps
can update roadmaps (add or remove roadmap cards, add or remove story map sources)
can comment, add and remove attachments
can add or remove observers
Observers
can open roadmap cards and see status reports
can comment on roadmap cards