Boss GP-10 guitar synth setup in Producer

I have the original Roland GR 50. I would hope the latency of the new systems is a little better. But my guess is just like using a digital drum kit, depending on your system etc, they might still be enough latency to throw you off. This is not a big problem for me. With both my Drums and the GR 50 I simply monitor the "brain" while laying down a midi track to Sonar. 
In other words, if I was to monitor the playback of a triggered soft synth, I'd experience enough latency ( delay) to make it hard to play in time. The GR-50 is very noticeable. 
So pick a patch from the Roland sounds that is close to what you want, record your part, then set the track output to a soft synth.
I have my outputs form the Brains patched to inputs 3/4  of my interface via a small mixer. So hopefully your interface has good monitoring/ patching capabilities.  
The reason Roland designed the system in the first place was to avoid midi latency. From day one using another MIDI synth module always resulted in a delay of triggered note. You had to use the Roland GR 50's sound module for your sounds. 
ANyways give it a try it's no different that triggering soft synths with a keyboard controller, just a different input source. Example, you can play a piano with my Yamaha DTX drums,,, very badly however...