Sam, I’m sure Accuphase makes excellent products, but, it’d be an awful waste of dCS’ Ring DAC to be putting the Rossini’s output through an A-D/D-A stage (especially one that uses merchant ESS DAC chip) 
If you look at the functional block diagram of the DG-68, you’ll see that it can do everything you want it to do, completely in the Digital domain!
You really don’t need to use the DG-68’s A-D/D-A stages at all. Meaning, you can equalise your system in the digital domain, and send its processed digital outputs to the Rossini and onto your Pre-Amp, in other words; DP-560 --> DG68 --> Rossini --> Pre-Amp --> Amp.
The DP560-to-DG68 HS-Link2 can remain a separate path to your Pre-Amp on a separate line input, and all your other Digital sources would go to the DG-68 instead of the Rossini, which would then be just a pure DAC for the digital output of the DG-68 (which is exactly what dCS’ are renown for 
)
You’ll still be able to enjoy the full digital-signal-processed/equalised benefits across the entire chain including with the Rossini inline. So, the steps to equalise your sound would remain exactly as described by Accuphase. 