Just to jump on this thread I also have the same issue when playing any ripped movie from my NAS. I have tried all of the suggestions here as well and no luck resolving it. Somehow the Roku media player is pulling the descriptive audio track even though it is turned off in the Roku unit. I have also tried running movies through my Sony blu ray and have never had this issue. The only way I have found to counter this is to convert the blu ray to an IPad compatible file (mp4) and run it that way....of course you throw out about 22gigs of useful data that way!! If anyone has any ideas I would love to hear it and it looks like many other folks would appreciate it as well!
The Audio Guide and a descriptive audio track are two completely different things. The setting for the Audio Guide will not affect which audio track is played from your ripped movies. I've never figured out the logic of which track the video player will choose by default especially if there are 2 or more labeled as English (I can't say that I put too much effort into it), but you should be able to choose the audio track by pressing the * button on your remote. I've gotten into the habit of only having one English track and then just labeling the others (like director's commentary) as different languages. If you'll never listen to the descriptive audio track then why include it in the first place?
This really doesn't belong in this thread. One of the many RMP threads would be more appropriate.