We received a request to pair a very old plasma TV without HDMI connections to vintage Roku XDS 2100X via the 3.5mm component out port. With no component cable provided and a replacement long since gone (technically) from the Roku site, some research was at hand.
Most sites list the XDS cable as "The component video connector on the Roku XDS (2100X) is a nonstandard 3.5mm connector and a proprietary adapter cable", which is somewhat misleading. In reality, the 3.5mm end is a standard 4-pole TRRS style A/V connection found on the majority of 3.5mm to RCA white/red/yellow cables. The fact is you can use a 3.5mm A/V cable to replace the component cable once supplied by ROKU.
Here are the pin-outs for both cables:
Tip = Green
1st Ring = Blue
2nd Ring = Red
3rd Ring = Shield/Ground (outer ring on green/blue/red)
Standard 3.5mm to A/V
Tip = White
1st Ring = Red
2nd Ring = Yellow
3rd Ring = Shield/Ground (outer ring on white/red/yellow)
Some A/V cables have the red/yellow connectors reversed, so keep that in mind. A quick test with a ohm meter can sort that out. Or just swap the two ends if things are not working out.