Clustered Storage Spaces Virtual Disk for Hyper-V - apply to role or use as CSV?

It is not only vague, it actually doesn't make sense. What is your topology, and what specifically are you confused about?

When I right click a Cluster Disk, within Failover Cluster Manager, I have the option to "Add to Cluster Shared Volumes" or "More actions -> Assign to another Role".  I'm trying to decide between these 2; the topology is a 3x SAS JBOD and 2 cluster nodes with 2 SAS connects to each JBOD.

Keep in mind that a cluster can host non Hyper-V clustered roles. If you are looking at Hyper-V or a SOFS then there is no reason to add the storage to another role. Just make it a CSV.

As an aside, CSVs are *only* supported for Hyper-V, and in 2012 the file services role for a SOFS. But the two would also never coexist on the same node and that configuration is, in fact, specifically called out in documentation as unsupported. I mention this because you mentioned SOFS and SMB3 in your original question, but your follow-up with hour topology doesn't seem to require that complexity.

Thanks for the clarification.  I guess it would be more accurate to says that this is a 2node dedicated SOFS cluster, with the intention of storing the Hyper-V VMs.  The Hyper-V cluster management will take place elsewhere.  Does that change anything?  I guess I don't really understand the difference between making this disk a CSV or assigning it specifically to the SOFS role.