That's not my responsibility now, but in past positions my Quality Systems team would conduct and document an annual review of third party standards/directives to see if there had been any updates since the last check. If there were, we'd acquire the new document and review any procedures that were guided by the standard/directive and take appropriate action.
There are also services out there that will monitor this for you, for a fee.... they will notify you when a rev is changed and you can take action immediately.
I kept form letters for REACH and RoHS declarations and just sent them out as requested. Some customers want the parts that they purchase from you on the declaration so I would accommodate that if needed.