Well to answer both questions:

I have 24 Gb of memory... Poser rarely uses more than 8.5 Gb when the bucketsize is set to 64.... I'm trying a larger bucket size now and using the queue manager so their is less over head with screen refresh

The exr.files vary from 14 to 20 mb -- exr is a hdr type [I read somewhere it originated with Pixar Renderman] but as the render progress it apparently is writing and re-writing this file... the exr is what is displayed in your 'saved renders'

As to roaming verses local profiles and temp folder. -- In reality they should have nothing to do with one another... unfortunately it seems that the programmers at SM fail to see it that way... and so the temp folder setting is nothing but something left over from pre-Vista times...it actually might work on XP but I'm running Win7 x64 SP1

Look at it this way -- the temp folder does NOT need to be attached to the windows profile. there is nothing in there that is either harmful to 'userspace' nor is it likely to be used for subversion of security.... much like the runtime... I've never put the runtim in my user space because It makes it hard to move when I upgrade... so runtimes are never on primary OS drives... and frankly I don't see whay the tempfiles are any different... oh yse the saved renders are in there and yes for some reason

I've administered Windows networks and workstations since 1996.. and know a little about it [maybe not enough being a general specialist ;)]... this looks to be an "undocumented feature" that is weighed down by the MS idea that application data should be attached to user profiles when 'temporary files' are application resources not user resources.