Hi @Jessica Cote,
The screenshot you're showing is of the standard Roadmaps offering and not Advanced Roadmaps. This might explain the differences between what you're seeing and what you're expecting? Advanced Roadmaps is available with Jira Premium and is accessed through the "Plans" menu in the top navigation bar. I've mentioned this because you've posted this question in the Advanced Roadmaps section of the Community.
However, this might just be a general question about the the implementation of the standard Roadmap interface, in which case I can get someone from the Roadmaps team to address the question.
I am a Product Manager from the Roadmaps team.
Thanks for providing feedback.
I think you are expecting a visualisation of Epic's child issue on the roadmap.
Currently, this is not possible.
However, you can vote for this feature here: here https://jira.atlassian.com/browse/JSWCLOUD-18668
Let me know if I can assist further.