I am not familiar with the Roberts 370. In Oz the Roberts 38 is a lot more common, often called the Offshore. Take it you have seen this website? (goto "Sailboat Plans" then "Sailboats from 30 to 40ft" then click on "Roberts 370" and there is some pretty pictures)
In the newish built compared to the older model one issue is the quality of the build. The vast majority of Roberts are amateur built and they can range from very good to bloody awful. I would get details of the original builder and try to assess their experience / reputation. A good surveyor would be the way to go.