a few years ago, Nextcloud announced a "basic integration" for Rocket.Chat into nextcloud that was very limited.
Now, nextcloud announced a deeper integration in nextcloud that we tested in the last days. The integration is easy, works with nextcloud users, document sharing and much more is possible. You can read more on the nextcloud blog: https://nextcloud.com/blog/rocket-chat-nextcloud-integration/
The app is available in the nextcloud app store with a screenshot: https://apps.nextcloud.com/apps/rocketchat_nextcloud
We have added Rocket.Chat services again on our website: https://owncube.com/rocketchat_en.html
With a active nextcloud and Rocket.Chat service, you can "connect" them very easy to extend your cloud functions, chat, sharing,...
If you have any questions, just let us know.