Prebuilt: Fixed wrong role change on remove from stage

[stanwolverine]

Description

When a peer is removed from the stage, it should be assigned its previous role.

Pre-launch Checklist

• [x] The Documentation is updated accordingly, or this PR doesn't require it.
• [x] I updated/added relevant documentation (doc comments with ///).
• [x] I listed at least one issue that this PR fixes in the description above.
• [x] I added new tests to check the change I am making, or this PR is test-exempt.
• [x] All existing and new tests are passing.