I am looking for a sword and sorcery book titled Raum. Author is
unkonwn. Can you help me please?

I believe you are looking for "Raum," by Carl Sherrell (ISBN:
038001646X). Here is a brief synopsis:

"He challenged the fury of Lucifer's Reign!  Brought to the world of
mortal man through the evil incantations of the powerful Jord, the
mighty warrior Raum battled through the frigid wastelands of
Everspring...defied the bloodthirsty Viking hordes...felled the finest
knights of Camelot...and matched his powers against the magic of
Morgan Le Fey in his quest for the sorcerer Merlin, the one mortal who
could wrest the centuries-old burden from Raum's great shoulders.  But
Raum paid a terrible price for his visitation to the world of man.  No
longer would he be invulnerable on the field of battle.  No longer
would demon-like powers of sorcery be his to command.  And as Asteroth
had warned, he was about to face that which made mortal man most
vulnerable."

Pywrit: Raum by Carl Sherrell
http://www.pywrit.com/ebooks/sfs_z/CarlSherrell/bi/raum.htm

Here you'll find a selection of online merchants offering the book:

Addall.com
http://www3.addall.com/New/submitNew.cgi?query=038001646X&type=ISBN

Addall.com
http://used.addall.com/SuperRare/RefineRare.fcgi?id=040718111828025925 

Google search strategy:

Google Web Search: "raum" + "carl sherrell"
://www.google.com/search?hl=en&ie=UTF-8&q=raum+%22carl+sherrell

I hope this helps! If this is not the correct book, or if a link
doesn't work for you, please request clarification; I'll be glad to
offer further assistance before you rate my answer.

Best regards,
pinkfreud