When creating a scrum of scrum board, linking 4 projects into a larger program, is there a way to view the epics for all projects on the scrum of scrum program board roadmap.
In addition to what @Tansu Akdeniz stated. By default - a SCRUM board's filter query drives the content of your board. So if the query itself pulls content from multiple projects, then all related Epics from all related projects will automatically be pulled.
A keynote of a board containing multiple projects content, then users (who need to create/close sprints) will need to have "Manage Sprints" right from all of the projects used within the board. Lastly, you should also need to ensure that all users who access the same board should also have access to all of the project too.
Hope this helps.
Best, Joseph Chung Yin
Jira/JSM Functional Lead, Global Infrastructure Applications Team