at npmjs.com/package/nodebb-plugin-dice-and-numbers
Built to work in the default composer. Not much css attached, but it should be pretty easy to make it look however you like.
Adds a button that opens a panel where you can select if you'd like to roll XdX dice or generate X random numbers within a range of X to X.
Results are visible in posts like this:
Results are also not editable in posts after they are rolled.
Still kinda wip but no guarantee I'll work on it further, since it does what I want for my own forum.
known weirdness:
if you have a thread where the last post has a dice roll in it, and that post hasn't been edited for a few months, the value can disappear. re-editing the post makes the value appear again.