Since when were roadmaps an engineering tool. Been an engineer for decades and roadmaps were never part of engineering. They are a PR tool to inform people what still has to happen in a project and engineers don’t use them.
Some come with both where the project is going and timeline, and others simply have where the project is going (similar to real road map)
When timelines are included then its a project management tool for reporting to management. What I gather a lot want is the gnat chart.