What is the impact on domain if the rid fsmo role is down?

Temporary loss of the RID master is not visible to network users. It will not be visible to network administrators either, unless they are creating objects and the domain in which they are creating the objects runs out of relative IDs (RIDs). RID will assign a pool of RISs to domain and in absence of RID, if this pool is finished, admins will not be able to create new objects. If RID is irrecoverable in either way, we can seize the role. But once the role is seized to other server, the old server should not come live on network.