If nobody else wants to do it, I might take a crack at it. Google Photos is a pretty impressive offering and the old PWA API still seems to be able to get at most of the underlying data model.
I plan to add a screensaver to my Picasa2 channel. Unfortunately, it may be a few weeks before I get to it. My computer broke, and I'm waiting for a new one to come from China, so I'm not doing any Roku development right now. Once it arrives and I finish off a couple of other projects, I'll get to work on it.