The C5 is probably one of the best towcars you could have, even if it is made by Shitroen
. It should have no problem pulling your roadster on a trailer. People get very hung up on BHP figures but to give you some perspective my camper is a 7 metre 4.2 tonne GVW Iveco with a 2.8 litre turbo diesel giving 100BHP and it will tow my 4.5 metre 1500KG trailer at 60MPH all day long (well except for uphill of course) and still gives 23MPG while doing it.
D.