I thought I'd pass on the tips I have got from my local RR operator, so that people going down to Northampton will be prepared. I know that most of this is common sense, but it is surprising the number of times he has seen mistakes.
1. Check your tyre pressures, especially the driven wheels. The rollers have two points of contact on the tyres, so the tyres will be working harder than they do on the road. Ideally you want the pressure set up for motorway/high load driving.
2. Check all your fluid levels. Oil, Water especially. The car will be running under load with reduced airflow to the radiator(s) so it needs the cooling system to work as efficiently as possible.
3. Check the fundamentals. Is the HT leads, plugs, distributor cap (??) in good condition. If not the car may lose power. Pointless forking for a session to be told that a plug needs cleaning or something equally as daft.
4. Cam belt. Very important. If it is not within the service interval some operators won't let you do a power run. If it snaps your engine may well be going home in a bucket.
5. Fuel. When the car is running on the rolling road it will be doing 80 or 90 mph in top to find the peak power. Don't turn up running on fumes. Just because the car isn't ACTUALLY moving doesn't mean it isn't burning unleaded like it normally would (I have witnessed this happen)
6. TRACTION CONTROL. If you don't know how to disable the system you are not going to be able to run. On most cars, even with a TC switch to turn it off, the ECU for it will fault and cut power if the rear wheels are static and the fronts are doing 70 mph. This is true on the Astra G, so make sure you have a screwdriver handy to pull the relevant fuse to shut down this function.
If anyone else knows of other relevant things I haven't covered, please copy and paste the thread, adding to it.