The Rogue Talent "Dispelling Attack" (Su) normally has a caster level equal to the rogue's level. Is this caster level affected by
a) the "Magical Knack" trait ?
b) the "Practiced Spellcaster" feat ?
c) any wizard/sorceror levels the rogue may have ?
Keep in mind that Dispelling Attack is a supernatural ability. Its not a spell like ability nor does it give the rogue the ability to cast spells. That being said:
a) Magical Knack would have no effect on Dispelling Attack, which is a supernatural ability. Magical Knack would raise your 'rogue caster level' by 2. But rogues don't get any ability to cast spells (even the minor/major magic traits are spell like abilities, not spellcasting). So taking Magical Knack for rogue would have no effect whatsoever. Dispelling Attack says to use your rogue level as the caster level for the effect. Magical Knack doesn't increase your rogue level any, so it would have no effect on Dispelling Attack.
b) Practiced Spellcaster requires that you pick "a spellcasting class that you possess." Rogue is not a spellcasting class, so Practiced Spellcaster can't be taken for Rogue levels. Even if it could, the same issues would apply as for Magical Knack, rendering it ineffective in boosting the caster level for Dispelling Attack as well as major/minor magic.
c) Dispelling Attack says to use your rogue level as the caster level for the effect. Adding a level of wizard or sorcerer does not increase your rogue level, so doing that would not increase your Dispelling Attack caster level.
Given that those three are out, in what way can the caster level for the dispelling attack supernatural ability be raised ?
none that I know off, I suppose this is where it pays off to stick with rogue single class. It is a fairly powerful ability anyway, I would not want to beef it up more as DM.
Yeah I don't really see a way to boost it up without simply taking more rogue levels. But thats like a lot of such abilities really. Many of the cleric domains have abilities dependent on cleric level...same with wizard specializations or sorcerer bloodlines.