|I agree you should have at least two writable DC's. If you lose the one writable DC, you could open up a world of problems.|
Do you want the admins at the branch office to manage the RODCs, or do you want them to manage the user accounts at those divisions?
If you want them to manage the RODCs themselves, you can make them admins of the RODC, if you want to give them full access to the server. If you want them to only manage the accounts at those divisions, then you can delegate control to those accounts.
It depends what you are looking to do. Try to be a bit more clear in what you need exactly.