Kill Ras:

Jump off the bridge at the begining, and die(be naked).
Click logout and then click release with 1 second left on your logout timer.
Rez up on the other side of the door, and proceed down to Ras.
Have your pet stealth to ras and attack.
He shouldn't pull the other groups.
You then can kite him around the miniboss area.

Go to alchemy lab:
1. Enter Scholo instance
2. Jump down the bridge far right so you die as close as possible to the viewing room
3. logout, press ressurect at 1 second (as described above)
4. Rez in the viewing room
5. Go down to Ras' room
6. Now there are 3 mobs at the alchemy lab: 1 spectral + 2 humanoid casters. As a rogue you can kill them all with a little waiting time: sap on caster, attack the spectral, use all your specials. Vanish when the spectral is dead. Then sap the higher lvl caster again, kill the other one. Finally kill the last caster. You always should wait till your vanish is up again. Maybe you need 1-2 Major Healing Potions.