[Sorry in advance if question already is answered]
Is there really need for range: Voice when targeting people inside a room or structure as in Scent of Peaceful Slumber (p 152)? My interpretation of the rules is that if the caster is touching (i.e standing inside) the room/structure he will also be able to affect whats in it. Given that the spell has a range of touch of course.
Have I missed something? Can somebody please clarify?
//erik. first post
You're absolutely right.
Wth range Voce, the caster can however be a bit from the room in question.
Exactly, with Range Voice you can cast the spell through a window on the other side of a courtyard, or down a hallway, or something similar.
All good.
If said spell (Scent of Peaceful Slumber) is cast with Range Touch, with the caster inside the room, must (s)he make a magic resistance roll to resist his/her own spell?
//erik. back to work
Magic resistance is never rolled. But he has to resist his own spell, yes.
Spells don't know to "miss" the caster, unless the spell is specifically designed that way. Especially "area affect" effects, like Target:Room or such. Cast a fireball, it's all over the place, an equal opportunity hazard.
Some canon effects are specifically designed this way, but the examples are few. CrIg Coat of Flame is one, with a Rego requisite to keep the caster safe. A similar end result might be achieved by the addition of the ever-popular "+1 Magnitude: Complexity", to create "a hole" in a large effect, centered on the caster (but if the Caster moves, the hole doesn't know to move with them!)
SG's should take care to envision exactly what a spell effect does, and warn their Players against something that is just an obvious mistake. If the Player/Character insists despite the warning, then you should just let them have it - literally and figuratively. 
Just to be clear to those new to the rules: the +1 magnitude would have to be incorporated into the spell when it was designed/invented - it can't be done on the fly for Formulaic Spells.
It also usually take a Rego requisite.
Often it's easier to just cast you T: Room spell forcelessly (meaning: penetration = 0). That way you won't be affected.
Ofcourse, neither will anyone else with MR...
Then again, my experience is that Room/Structure/boundary often is most useful on dealing with multitudes of mundanes. All else is suicide. 
//erik. muscle spasms in left foot
exaclty!