It is more difficult than I thought because there are thousands of Bubecks from Rotenberg and my uncle said that a lot of them immigrated.
I think it is quiet hard to find something out in just half a day - by the way your cousin should go to the Protestant archive in Möhringen because you don't get the information in the tiny little church of Rotenberg or so. Anyway, here is the link of the English version of the homepage: http://www.archiv.elk-wue.de/cms/startseite/family-research/
But it is really hard because of the handwriting (as you can see in the example picture).
I'm still wondering if our ancestors were realted in any way but I don't know when I come to the archive again.
I've learned that from our closer family it was Emil Luz who went to Australia (area of Perth).