This is a very simple python script that you can cron job to clear history from a rocket.chat server that are over 30 days old. Use at own risk under GNU public license.
https://www.gnu.org/licenses/gpl-3.0.en.html
Simply use this and add it to cron to have it clear any chat history past 30 days old.
#NOTE You will have to change localhost/parties to the name of YOUR DATABASE name for this to work. You can change the threshold from 30 days to anything by modifying line 25.