Roadmaps fail when they pretend to be promises. Treat the roadmap as a statement of current intent, ordered by confidence, and it stops being a stick people beat you with later.
Group work by the outcome it unlocks rather than the feature it ships. Stakeholders argue endlessly about features but tend to agree quickly on outcomes, which makes prioritisation far less political.
Revisit it on a fixed cadence so it stays honest. A roadmap that never changes is not a plan, it is a wish written down once and forgotten.