In manual for YSD600 door system, YKK part number for tandem roller is E1-1620.
Do you have an equal?
I am afraid I can't cross-reference those part numbers to any specific roller. Patio door hardware is incredibly varied and independent of make or brand. The only way to reliably say what rollers you need is to see them out of the door. The width and height of the assembly and the diameter of the wheel(s) is also necessary. From there, we'll do our best to find a match for you. Thanks.
I'm afraid we never came to a satisfying conclusion for this discussion. We may still be able to help, but we will require the requested information above: a clear and unobstructed photo of the roller in question removed from the door. We would also need detailed and written dimensions that we can use as a reference.
I can't guarantee that we will be able to supply this roller, but we will do our best.