Where do I make a feature request to drupal.org?
Generally speaking, the correct place to post feature requests for Drupal.org is the Drupal.org customization project issue queue.

However, you also wrote:


  FYI - I'd simply like to suggest that project owners have a tab for "roadmap" or "project Future".


If you just want to suggest that project owners publish a "roadmap", you can add that suggestion to the community documentation. It is a wiki so you don't request anything - you just do it (like I just did). 

If you want to actually modify the project page layout by having a feature where project owner's may add an addtional tab for "Roadmap" to the page summary, you request this in the Project module's issue queue 

Finally, I shall not suggest you use the Webmasters issue queue for any type of feature requests.  The Drupal.org webmasters issue queue is for reporting spam, broken links, or user account problems at Drupal.org - and that is about it.  My experience is that nothing much happens to feature requests posted there, even if the request just involves flipping a trivial setting in a module already installed. The webmasters obviously have the power to do this, but they do not make decisions about such things.  They usually move feature requests to the Drupal.org customization project, and bug reports to the Infrastructure project.