Flt Lt Mac, is this a pre OASC tester?
According to the RAF website, the C-130K operates with a crew of 6, therefore I will assume you are referring to the C-130J (I had to put that in in case you trying to trip me).
This is what I believe the role to entail, as I have understood it from the literature, media and people I have read, watched and listened to:
A WSOp on C-130 is responsible for the majority of what happens behind the flight deck. Specifically, the WSOp is responsible for the loading, safety and unloading of any cargo* or airdrop**.
*freight, supplies, vehicles, passengers, troops
**all of the above leaving the aircraft before the aircraft lands
Also the WSOp can assist the pilots in the aircraft's pre start-up checks and ensure the Hercules is safe, secure and locked after shut-down.
During the flight the WSOp will be available to assist the flight deck where needed, for example, comms.
I understand a strategic role as being proactive, therefore planned in advance of the flight. For example; a flight from Kandahar to Bastion to resupply ground troops with supplies such as food and ammunition. The WSOp will be able to plan how much food and ammunition is needed and how much the C-130 able to take. He will be responsible for the safe handling of the supplies.
I understand tactical missions as reactive, therefore an event will directly influence an immediate response. For example; During the flight back to Kandahar, the flight deck receive a transmission that they are needed urgently on the ground for a casualty evacuation. This will cause the WSOp to think on his feet and re-configure the cabin to accommodate casualties and medical team.
How did I do? I hope I passed...