Caoimhin O Donnaile wrote:

> Could the letters ‘r’ and ‘ϕ’ have been indications of who  
> was to speak each piece?

That's doubtful.  In the LU Táin (which is where the .r. on my blog  
came from), we have overt naming of the persona who speak the  
individual pieces of rosc.  For example:

.r. Cu Chulaind dixit ...

.r. Ailill dixit ...

In LU, however, the pieces of rosc ar not laid out as verse.  It's all  
written like prose: one word after the other, filling up each full  
line and moving to the next.  So the .r. does alert the reader to  
change gears.  "Attention!  This may look like prose, but it's not."