Hi Laura -
Sorry for the delayed response, here.
So, I'm not entirely sure I understand your question, actually. Once GNU Radio is running in Android, using blocks from any module, in- or out-of-tree, shouldn't be a problem as long as they are built appropriately. Are you asking if you need to re-write Python-only blocks in C++? If the OOTM only provides Python blocks, then yes, you'll want to put those into C++ for use on Android.
Also, I assume you've already seen the pages linked here, which provide a lot more detail on that build process -- although the information is pretty severely dated at this point, and almost certainly won't work as-is.
Cheers,
Ben