Seperate device vs software solution
This is a rather broad question and may get closed, so I'll be brief.

If you have a general purpose computer like the RPi in your system already, let it do whatever it can within its capability of direct I/O, latency, and bandwidth.

You don't say what the real time requirements of this radio module are.  If you are required to react with short latency, then a separate micro to do that makes sense.  If the module has sufficient buffering or whatever so that fast reaction isn't required, then the RPi can handle it.  This is assuming you have the appropriate I/O lines available on the RPi.