On topic,

"a modern single roller rolling road does not suffer with all the wheels spinning,loading the rollers problems that older style rollers do.

a dyno bench test is excactly what it says it is a BENCH test. Unless the engine has the correct mainfold and full system connected on the bench you will not get a in car output

a rolling road that doesnt give a accurate figure is still a good tool and aslong as you always use the same rolling road you will tell if any modifications you have done have worked. remeber if a rr is 10% out for example it will always be 10% out so you will see a improvement if there is one to be seen.

another good way of seeing how much bhp your car has is to run it at santa pod ignor the time but look at what the terminal speed is if its crossing the line at just over 100mph its got around 210bhp per ton is the general rule of thumb"