I don't have a YRG to check myself so I looked at the manual for some clues and came away
disappointed. No MIDI implementation chart !!! That's a total disgrace.
the reason I was looking for the MIDI implementation chart was to check whether the YRG
sent MIDI Note Off messages or not. The MIDI spec doesn't require Note Off messages but
makes provision for them. Some manufacturers use them, others don't. You can send a Note
Off message when a key is released, but alternatively you can send a second Note on
message with a velocity of Zero.
So I would suggest that the first step is to
look at the MIDI output from the YRG and establish exactly what MIDI messages it
generates. Not just to decide whether it sends Note Off or Zero Velocity messages, but to
find out what other MIDI controller messages are being generated.
suggest recording a section of your playing straight into your DAW as a MIDI file. Then
you can use it as a repeatable source for testing the FCB and Roland combinations. When
you get problems you will be able to compare the corrupted output with the original file
and work out if there is a pattern.
When the going gets weird, the Weird turn Pro.