Just put together a R2 weather node and had a compile problem.
The following line was missing from the R2 sketch in github. I was able to find reference to it in forum posts. Adding this line solved my problem.
#define SS_FLASHMEM 8
That line is not really missing, SS_FLASHMEM is defined in the Moteino board definitions (pins_arduino.h).
So as long as you have Moteino as target you don't have to include those definitions.