pre-amp unacceptable noise level?

Have you tried a cheater plug on your amp. Sounds like you might just have a ground loop.

If that doesn't work you might just need some low noise tubes.

What does the manufacturer say your problem might be? A very light hum or hiss heard from less than a foot from your speaker is not unusual IF you have very efficient speakers or an amp with a very high input sensitivity.

Another cause of humming can be from locating a pre-amp too close to a power source, usually an amp on which some people like to stack stuff (ever noticed how many high end pre-amps come with seperate power supplies often connected to the pre-amp by a long cable), and proper cable dressing, that is, making sure all of your IC's are not near any power sources or power conditioners. I've had problems with both of those issues. Easy to cure. BTW this is generic advise - I've never owned a Rogue.

Dumb question- Is the noise only present when you rotate the volume control to its maximum position? Is it quiet when the volume control is in a position when the music is at a 'normal level' or even a bit loud?

If the answer to these questions you are just talking about your units noise floor or the noise from the (in your case) connected CDP. The fact that you do not hear anything for 20 seconds indicates that the 'hum' comes from your pre-amp (or source) which is muted on initial turn on to avoid transients while your pre-amp is stabilizing.

Try disconnecting the CDP and see if the noise level changes. If not then its the pre-amp. If you hear the hum/buzz etc at normal volume levels at 10 feet you've got a bummer and should contact Rogue for repair or replacement.