A powerful new computer is able to brute force its way through all those routing errors, but I have the same experience with Roaring Height as the OP. If you look at the floor plans, you can see lots of one tile wide hallways or one tile wide entry ways to sometimes huge mansions. Layouts like that don't work in the Sims3.
Of course, if you just start the town and use a mod like NRaas SP, it will have to work through the whole town during the first sessions, which will result in the occasional freezes. Those will be gone later on.
Roaring Heights needs quite a bit of remodeling. For example, the many bars and cafes are in need of making them functional, other than as hangouts.
