Definitely a good suggestion from my perspective too, but the Roadmap link in the sidebar is a different type of roadmap: the basic roadmap that is restricted to a single project.
As a workaround, what you could do is add a custom link to the sidebar of your project with the Add Item option. Just name the link "Roadmap"and paste in the url to your advanced roadmap plan.
If that works for you, it may be a good idea to disable the project roadmap as well, to avoid confusion by having two different roadmaps links on the same board. That is something you can do in your Board settings, on the Roadmap pane.