This is currently under review as DE43599.
Option 1: Use the role replace feature in the New UX (User Experience) as that will prevent the role from being replaced with the same resource multiple times (there will still be a role remaining on the project with the allocation gaps that will need to be replaced with another resource available during those times, or manually update the resource allocations then remove the role from the project.
If using CA PPM Classic UI:
- Replace the remainder of the allocation that the role is on the project with a different resource available during the gaps the first resource was not available
- Manually update the resource allocations to the desired amounts, then remove the role from the project