The talks from the big Congress (yearly) are either in German or English. I'd say the split is 50%. But most talks are translated ton English or German and some are to other languages (French, Spanish, Russian). The translations are done by volunteers during the talk so they might not be perfect.

That doesn't guarantee this Roku channel will have those translations.

Usually it's represented in different Videos. If they offer all videos, the different language versions should be available.

This year at least, they're distributing them as a single video file with multiple audio tracks. No idea how Roku handles that.

All of this years talks are either English or have been translated to English. At the conference there were simultaneous translations. 100% de<->en coverage and few other languages, Russian, French, Polish and Spanish too.