If you put the same file on a USB stick, does it play?
What type of file? mkv? mp4?
Do any other files play? mp3? Is it just a single type of file?
A few people including myself who have been impacted by this issue are reporting back on the Emby forum http://emby.media/community/index.php?/topic/36572-movie-stream-stops-and-wont-resume/page-2#entry34...
There seems to be an issue direct streaming files that are over 4GB in size. I can confirm that all of my movies that are under 4GB work (I have tested like 50) and files over 4GB fail (I have tested like 20). I will try to cut down a few of my files to smaller sizes, while maintaining all the same quality and encoding settings to test this further.
squirreltown, are your files over 4GB? and on what Roku model are you using? It might be limited to the 4200 model.