Answer
Three views cover this: FND_USER_ROLE shows which permission sets are granted to a specific user or users; FND_ROLE gives details about permission sets themselves (like when they were created and what type they are); and FND_GRANT_ROLE shows the structure of which permission sets are granted to other permission sets (the hierarchical grant structure). These share common columns (like the permission set/role identifier) that let you join them together for deeper analysis of the overall grant structure.