WebRTC: start "screen sharing" conference

I hope this is the right category for this, but I was wondering. I tried Jitsi and WebRTC, but neither seems to allow this: Is there any way to start a (preferably webrtc) session with JUST screen sharing (where the other side can view it but doesn’t have to share anything themselves)? My use case is that this would allow rocket chat for quick remote support when users have a problem.

I’m sure rocket chat already has a way to do this, I just can’t seem to find it. Does anyone know how to do this?