...

Any piece of geometry can become a light source in RenderMan for Blender.   Always use Mesh Lights for objects with high light emission and always perfect for neon signs !

Select  Select the geometry that should become emissive and click on Convert to Mesh Light button from the object context menu.

...

When the Mesh Light button is clicked, a new material called PxrBlack is assigned to the selection, and a PxrMeshLight is created and wired into the material of the PxrBlack material.  PxrBlack  

PxrBlack acts as a dummy material.  It doesn't actually have any parameters.

For most purposes, PxrBlack is an appropriate material, but you can experiment with using others, like PxrVolume.  The easiest way to set that up is to begin with the Mesh Light button.  Then 

Then, select the shading group for the PxrBlack and wire in a different surface or volume material there.  This  

This way the area light is already wired into the shading group.