I don't understand what you want to do.
Could you explain ?

Hi,

I created 26 projects and now i want to create a roadmap with all these projects.
How do I proceed to create this portfolio/roadmap/release ? I would like to use your report but I don't see my projects.

Thanks for your help

Laurence

maybe create a "ghost" project and attach all your project as sub project ?

many thanks but you don't use a version for all your projets ?

Create a product (or several ones), create versions for this product (or these products), link projects to corresponding versions.
Then, when you define tickets or activities, you can link items to versions.
Here is your roadmap...
(have a look at track database to get an overview on how we manage ProjectOr roadmap 😉 )