Hoping not to come too late for whom is interested, I'd like to point to the upcoming
Rolli days on the 14-16th of October in Genoa, when many Rolli palaces open their doors. While it is true that one should book visits, it is also very possible to just go there and slip in the vacancies (I did so last year with great success). It is an exciting way to enter the palaces, mostly free! There are also special guided tours about Rolli.