I am experiencing this issue as well. I think the Disney app is a red herring, this seems to be a larger Roku Express issue.
For me this is happening for at least Hulu, Sling, and Google Play Movies on my Roku Express. I can generally go about 20-30 minutes before it takes me to the home page. Not that huge of a deal when watching a sitcom, but it's really a pain when watching an hour long show or a movie (especially on Hulu where resuming a show or movie tends to take you back before the previous commercial break)
I also have a Roku 2 that does not have this issue (and has never had it).