User roles combine all access attributes for a user in a single object, so it is more flexible than and manageable than separate ACLs.
This video series has in the start a nice explanation on the concepts in the first episodes.
Also note that you can have local user roles on the 2530. The feature that you won't have versus the 2540 is that you can't download the role content from ClearPass but you can configure it on the switch itself and return the role name from ClearPass.