I have rendered and replaced many clips in an FX-heavy music video i am editing in Premiere Pro, with the linked FX done in After Effects (hence them being rendered and replaced, to make it run smoothly in Premiere). Now when it comes time to grade it, I send it to Speedgrade via direct link, but the clips show up in speedgrade as the raw source clips, which in this case is a bunch of green-screened actors, which is obviously useless to try to grade.
I am guessing that Render and Replaced clips do not work in Speedgrade via direct link? If this is the case, what is the correct workflow?
Speedgrade has been discontinued, and has been neglected a long time. Its not surprising recent features added to Premiere Pro don't work in Speedgrade.
Maybe locate the media from the render and replace...import it and manually edit it into the sequence so that you are not linking to the AE comps. It will just look like a regular Quicktime movie that way. Do this on a copy of the sequence, obviously, so you don't lose the ability to tweak it again..
If you need advanced grading, I'd start transitioning to Resolve if the tools in Premiere are inadequate for what you need to do in future projects.