Roku isn't switch HLS bandwidths, but VLC and iPad are?

I made a test HLS stream with FFMPEG here:

http://www.perturb.org/tmp/hls/castle/

If I load that on an iPad or VLC it plays just fine, and switches bandwidths according to needs. If I point my Roku at that URL it always picks the bandwidth that's first in the playlist, regardless of actual bandwidth available. Any ideas why the Roku won't switch bandwidth?

There are 5 different bandwidth streams, for this content.