I don't think the gain control on the R9 adds noise unless you change it while recording. Then it does add a small click for each gain step. But they are subtle and easily masked by most program material, especially if the signal level is decent. The click are also audible when the AGC changes the gain, but since the AGC decay time is very short I don't use it.
I've talked to Roland USA and they know about it but so far have not responded with a cause or fix.
Paul