How much would you think is a good price for a so called mint condition rolled original poster of the film ???

Not my area of expertise, but I'll take a guess...

A folded mint U.S. poster goes for $50 to $110. So a rolled (i.e. no folds) original (which is rarer) should go for ~ $150. Maybe more.

Thanks for that, the prices you quoted for the rolled version are about what is being asked, thanks again.