I hear that you can merge mine rootstock coins with existing bitcoin mining hardware by doing merge mining. Is there a tutorial on how to do this? Or is there a pool one can just join?
The easiest way is to join a pool that merge mines what you want, in this case Rootstock.
If you want to run your own pool, make sure the pool software supports the type of merged mining you want to do. Then set it up as described in to the documentation.
Rootstock is not live yet, but many pools are testing it, so you should have several pools to choose from.