As it turns out, it would require some kind of active converter/transcoder to do this since the RGB signal is not already separate.
As stated by snips-n-snails, one could mod the Commodore 64 to output component RGB, then convert that signal using the Retrotink Comp2RGB. This would give me the best possible picture/output available.
However, if one doesn't want to mod their Commodore 64, there are several devices that clainm to take a composite (or s-video) output and convert that to RGB, which then could be sent to the RetroTink converter, then to SCART (RGB+sync).
Here are the two I have found :
Composite RCA S-Video to RGB Component Video Converter:
What's nice about the Koryuu Transcoder is it claims to transcode/convert video without adding any scaling, processing or input lag. I may test one or both of these devices and report back if one or the other works better.