Use this roshamuul monsters:
https://github.com/PrinterLUA/FORGOTTENSERVER-ORTS/tree/master/data/monster/Roshamuul
Change the ID of the corpse inside the monster file, and also just change the loot >_>
<monster name="Dragon" nameDescription="a dragon" race="blood" experience="700" speed="185" manacost="0">
<health now="1000" max="1000"/>
<look type="34" corpse="5973"/> -- look type (outfit) and corpse id...