Hello,
There is no need to manage any OR conditions as that is why you have the Roles_Departments mapping table there for.
E.g. Your Roles_Departments mapping tables might have values like -
Role_Id | Department_Id
R1 | D1
R1 | D2
R2 | D3
R3 | D2
R3 | D3
Now, if you pass the particular Role_Id you need via USERNAME(), the related departments will get filtered which will inturn all the related tables showing data only related to those filtered departments.
Hope, this will give you more clarity. If you still have any query, please do write back.