Greetings. I use an IPTV app (Web Video Caster) to stream video from certain sites. It works flawlessly in almost every case, the exception being Spacex.com (to watch the streaming launch videos). I reported this to the app owner and they had me check things, but reported that they pass the video content on to the Roku to play, and suspect the coded being used by Spacex.com is faulty. They noted that it's actually streaming from X.com, and they knew that in the past Rokus couldn't stream Twitter videos.
They suggested I ask you for information on this as the codec decoder is called by Roku software and not theirs.
If you have a streaming app, try yourself. An example video can be found here:
That link is an m3u8 file at 1920x1060. The artifacts mostly show at the bottom of the screen where the text and graphics are displaying telemetry (after launch).
If Roku didn't support Twitter videos, then that's likely the issue now. Roku supports the more common video codecs used by online sources, but we don't know for certain what codecs are being used by SpaceX. I was able to find some recommendations from X/Twitter that call for the MOV or MP4 container, H.264 video and AAC for audio. For live streams X uses HLS/AppleHTTP. Roku devices support all of those. But SpaceX could be doing something that has "tweaked" the video codec that causes issues with Roku playback. Since X doesn't offer a Roku-specific app, they may either not be aware their tweaks have impacted playback or Roku, or they might simply not care. I was disappointed when they stopped streaming live on YouTube, but there are other YT sites that still provide the live feed so that's still my go-to way to watch a launch/recovery. NasaSpaceflight is a good YouTube source for SpaceX content.
Dan, I have that option of course but in every case, it's like looking at what I want to see in the background while those pages talk and switch away. And not everything should be forced to YT either, they certainly are not the solution to everything.