The concrete tiles I think are cast from lightweight concrete, but still way heavier than wood shakes. The carpenters built the roof like it was only going to have wood shakes on it. Home built in '85 so there were not many hangers on the trusses… and not a lot of nails in them either.
The diagonal member coming up out of the lower left is the hip rafter… three nails, typical (see another hip coming up fromthe lower right, cut short and shimmed with plywod). Single cheek cut on a hip should have 5 nails, even in 1985.
Although the roof is mostly trusses, a lot of the common rafters (in the areas that had common rafters) seemed to have only 2 nails at the top cut. Hips should have been blocked between trusses (shot at the left) to provide plywood backing at the hip.
They clipped some of the rafters to the top of the wall, but not the hip rafters.
It’s a sizable house and there’s a lot of roof up there. Unless the sellers can come up with documentation from when the people they bought from switched from shakes to tile I’m recommending Structural Engineer. Even if they can come up with documentation of engineering, I’m still tempted to recommend a qualified contractor add fasteners and improve framing connections. Winds can gust up to 100 MPH around here.