During Reducation 001 Michael Cioni said the debayer capabilities of Redalert and Redcine were superior compared to Color debayer function and it would have been better to transcode the R3D files to other codec prior importing into Color. Also Color 1.5 still uses the old color science so if you want to use the new color science is better to adjust color settings in Redalert or Redcine.
This is our 4.5K HD FCS 3 workflow, it's highly subjective so just take it as a tip, if you have different solutions you are welcome.
1 Shoot at 4.5K (I use Profile SC 4.1 or you can use the standard Redspace/Raw 320 ISO)
2 Transcode with Clipfinder all R3D files to 720p 1k high prores LT
3 Edit in FCP
4 When finished export an XML
5 In Clipfinder choose import clips from FCP XML
6 In Clipfinder choose Tools - replace MOV with R3D
7 Adjust color settings and transcode the R3D files to 2k normal prores 4
8 In Clipfinder choose Tools - Run conform on FCP XML file and adjust sequence width and height to 1920x1080
9 Open the new XML in FCP and you should have a 1080p timeline with 2k prores 4 files that fit the sequence
10 Check sequence settings (compressor, field, render at 10 bit)
11 Send to Color and grade
12 Send to FCP, finish the project and export in the format you like for delivery