I also bought R:TW Gold. It is the one that includes Rome:Total War as well as Barbarian Invasion. Mine installed both versions of the game (RTW & BI) and RTW was already at ver 1.5. You can see the version somewhere in the menu system of the game (at work now, can't check).

So, to answer one of your questions. You don't need to patch RTW. It is already at 1.5 unless you want to try out 1.6 (the latest patch I believe)