You could take a look here:
http://fi.wikipedia.org/wiki/Roos_af_Hjelms%C3%A4terIt states that the family originates in medievil Norway (I think with either royal and/or noble links) & has later connections with Sweden.
It says the name is referred to in Norway as Sudrheim or Sorum, which would tie in with Jon Raud Ivarsson.
It would be interesting to hear what you know so far & what you need to find out, since this family dates back so far I assume you have a fair amount already?
Are you located in Scandinavia or in the UK? Just makes a difference as to which resourses might be most useful to you...