A roadmap is a list of things you said yes to. The inverse roadmap is the list of things you said no to, and it is often the more strategic document, because it forces the team and the company to be explicit about the trade-offs that yeses imply. Most companies never write this list down, which is why the trade-offs are constantly relitigated.
What to put on it
The big requests you turned down this quarter, with one line each on why. The strategic directions you considered and chose not to pursue. The features customers ask for that you have a clear reason not to build. The market segments you are deliberately not targeting yet.
Why it matters
The inverse roadmap turns the strategy into a forcing function. Anyone who wants to reopen a no has to explain what has changed. Anyone who wants to add a yes can see what the trade-off implies. It is the document that protects the focus the roadmap claims to have.
How to share it
Publish it internally. Most teams find that the conversations about the inverse roadmap are more productive than the conversations about the roadmap itself, because the constraints are finally explicit.