A question about including libraries
Firstly, to address your compilation error:

RadioComm rComm();


That is not a constructor, that is a function prototype. When you have no parameters to a constructor you must not include the brackets or it confuses the poor little compiler.  

RadioComm rComm;


Now - to address your main question.  Well, there's many ways of doing it, but the way I always tackle this is to have your sketch define the RF24 object and pass it to the library for later use.

In the class definition, in the private section, add:

RF24 *radio;


Then change the constructor to have:

RadioComm(RF24 &amp;r);


The constructor itself would then read:

RadioComm::RadioComm(RF24 &amp;r) {
    radio = &amp;r;
}


Now throughout your library, instead of working with radio.whatever you need to work with radio-&gt;whatever since you are now using a pointer to an object not the object itself.

Then in your sketch you need to adjust your constructor to be:

RF24 myRadio(7, 8);
RadioComm rComm(myRadio);


The beauty of this is it decouples the configuration of the RF24 class from the RadioComm class, so you can use the same library in a different situation on a different board with different pins without having to change the library - just change the RF24 constructor in your sketch.

It also gives you direct access to the RF24 class in your sketch so you can do any advanced manual tweaks outside the library should you wish to.