We are setting up for Role and Department based planning, forecasting, actual transactions tracking. Prior, we were only using Transaction Class, where classes described labor by region (USA, Germany, etc.).
Our uniform list or roles is going through an update. Our roles have been global and this will remain - we are only updating role names, consolidating some, creating some new.
One thing that is different is that we will now have 3 levels of roles - grand-parent, parent and primary. These 3 levels were desired for reporting purposes.
One problem: The browse role lookup windows display all roles, regardless of level, not just primary. This is a problem if your parent and grand-parent roles are intended for grouping purposes in reports, only - nothing prevents users from assigning these to resources, team and/or task roles.
Tired of waiting on CA to allow customer configuration of system provided lookups, we gave up - we modified our role lookups so that they only present primary roles to our users for selection. Yes, it means we will have to restore the original lookups for upgrades, troubleshooting, etc. and then put our modifications back in afterwards. But the errors produced by letting users see/pick things they were not supposed to were not surmountable through training and surveillance - these are non-value added activities when one can Poke-Yoke the system to prevent user errors!
We've tested the creation of Cost Plans using primary roles allocated to Team\Staff, with Department OBS values select in Staff OBS column and Department based labor rates in Rate Matrix - works perfectly.
Your probably already considering this, but you didn't mention it, so I'll mention it here, just in case: Skills. If the skill sets for FX and OT are different, then you may need separate roles. In our world, the skill sets for an Engineer-Mechanical working on a brake rotor can be quite different than an Engineer-Mechanical working on a anti-lock brake valve system. If you don't intend to use Skills feature, this may not matter.
Looking forward to hear what others are doing. Good topic!