Remember that per Cascade's Org Structure on the Profile > Organization page, Roles are aligned to Org Units, and Users are plugged into Roles.
All ownership of goals in Cascade happens at the Role level, and not the User level. This is extremely important to keep in mind when looking to delete a Role.
Before deleting a Role in the Roles section using the "X" at the far right, first use the paper airplane button to make sure there aren't any important goals to shift away from that Role to someone else.
Remember that when a Role gets deleted, any goals assigned to it are also hard-deleted and cannot be retrieved. See this article for more information.
You can have an unlimited number of non-login Users and Roles in your system for the purposes of reporting, so having extra Roles doesn't really do any harm unless you just prefer to clean up your org chart.