It's kinda odd that the file isn't in it's own directory of some sort and is just dumped into the 'Roaming' root. That's pretty rude nowadays but still happens. It could also have been used by something other than RA(bloatware, free trial, etc).
You could try 'renaming' it (racore.dll) to see what breaks until a reason is figured out why it's there and running. You will have to find out where/what is calling that rundll with racore.dll being passed to it.
Notice a pattern? --
one should not increase, beyond what is necessary, the number of entities required to explain anything