Grimy rogue's purse is a herb that is obtained by searching the walls in the cave to the north-east of Tai Bwo Wannai village by the harpie bug swarms, as a drop from a jogre or tribesman or during the Shades of Mort'ton quest. It can be cleaned to obtain rogue's purse.
It is the fifth and final herb Trufitus asks players to bring him during the Jungle Potion quest. If the herb is dropped by a monster, Trufitus will complain that the herb isn't fresh and that you must find one yourself.
Rogue's purse is one of the herbs that can be given to Fycie and Bugs to 'Ogre-boat' players to the Chompy bird/Jubbly bird Hunting spot, provided they have completed the Jubbly part in the Recipe for Disaster quest.
It is also one of the ingredients to make Relicym's balm.