It was the dynamic art tagging that was messing up alac streaming to the roku. My note to RokuMike:
Fixed it. The problem was I had art_filename set to folder.jpg. For some reason mt-daapd thought it needed to add the album art (which it didn’t because it is in the m4a tag). It messed up the file by doing so – the alac files were fine until mt-daapd futzed with them. Commenting it out of the conf file fixed it.
Note this is unrelated to the fast start info issue which some alac files have.