This feature is available in Ultimate edition only.
From the main menu, select Portfolio Planning > Roadmaps.
If not already selected, choose a project from the Project Navigator.
Click on the Board or Timeline layout button.
Select a roadmap from the Saved View drop-down list.
Select Update Publish > Published Roadmaps.
In the Published Roadmaps dialog box, click Delete next to a roadmap.
Deleting a published roadmap also deletes all earlier revisions of that roadmap.
This feature was added in the Winter 2017 (17.0) release. It is not available in older versions of Lifecycle.