It should work just fine. Any type of memory (micro SD's included) are one of those "you get what you pay for" types of items. Patriot is a solid brand name.
Some folks will say that class 4 isn't fast enough, but believe me, it's just fine. If you eventually plan to try running other Android systems from the SD, you might want to consider a class 6 card, but as storage it is just fine to use class 4 or even 2 really.
Not until we get 2.2 or higher on our NC can we take advantage of the Apps2SD function, so the only thing your SD is doing for now is storage.
Any micro SD card size at any speed will work for rooting. Speed more comes into play when you are using a SD card for file storage or operating system running.