Can I save an alpha channel when Exporting Roles?

So I have my roles organized in FCPX and I am exporting as ProRes 422 which should support alpha channel. When I reimport the clips that are made to a new timeline, FCPX doesn't use the alpha channel. Is there a workflow for this?

I figured if the role had no data during a certain timecode range it would be transparent, but instead the exporter outputs black. Do I have to go ProRes 4444, or what about this option of sending the exported clips to Compressor? I figure if it is overlaying black during the export, when it gets to Compressor the damage is already done.