The argument you made with Rock Band you can make with ANY console game. In order to play any Wii game you need several peripherals, in order to play a 360 game you need to buy a controller... The need to buy the equipment up front is something that is given for some console games, hell even Duck Hunt needed the Nintendo Laser Gun (which, if you were like me and broke the one it came with, you needed to buy another one). Also World of Warcraft has only ONE extra cost at this point in the form of Realm Moves, with a second coming along the way in the form of changing you Race/Side. However both of these costs have no actual impact on in game play or cause a ripple effect, where if you are the one WITHOUT that thing then you're SOL.
I'm also skeptical that Bill Roper used these two games as examples for micro-transaction games in the US and avoids using the obvious example if Second Life. Second Life is a game that has micro-transactions truly integrated into it's game system and is well known to his target audience. Second Life as a good example of a free to play system where if you really want to get into the bones of the game than you need to shell out some cash.