I have been playing catan for at least 6 years, following a trip to the Netherlands where I encountered the game. For the whole time, I have played that, on a role of 7, the player cannot build or deploy dev cards, in addition to the robber business.
Recently I have checked the rules site and been disabused of this notion. Have the rules of Catan been changed at all since its creation?
I have a strong recollection of checking the rule book and verifying that one could not use dev cards on a 7 role, but I could well be delusional.
I enjoy playing with this set of house rules, but it is useful to be familiar with the RAW when you play with new people.