Sure you can put all the files into the same bucket and even the same folder in your bucket if you like.
From the docs -
StreamBitrates - roArray
Array of bitrates in kbps for content streams
[384, 500, 1000, 1500]
StreamUrls - roArray
Array of URL's for content streams
["http://www.myco.com/vid/1932-1.mp4",
"http://www.myco.com/vid/1932-2.mp4",
"http://www.myco.com/vid/1932-3.mp4",
"http://www.myco.com/vid/1932-4.mp4"]
StreamQualities - roArray
Array of Strings quality indicators identifying a stream as "SD" or "HD"
["SD", "SD", "SD", "HD"]
If your channel is loading/parsing all that from xml then roku will determine which bitrate to play which is associated with which filename. You set the bitrates, you set the urls, you set the qualities, and roku does the rest.
http://sdkdocs.roku.com/display/RokuSDK ... +Meta-Data