The rogue skills (not really "rogue only" since they're shared by bards) aren't so much 'needed' as much as somewhat useful. Most groups tend to ignore floor traps as they're usually not detrimental enough to seriously hurt, but if you have the skill it definately helps. Same with chests; if there's no rogue you usually ignore them. If you have a rogue, you give it a shot. Chest traps are much nastier than floor traps, by the way so few groups are keen on trying to bash their way into chests and boxes (besides which, bashing usually destroys the contents).
The nice thing is that you finally get a chance to
use the skills. Outside of Dragon Necropolis and some places on Luclin, there wasn't much chance or reason to sense/disarm traps prior to LDoN. And pick lock serves a purpose beyond getting random invites to CoM reaver raids
It's even nicer for bards; prior to LDoN, our skills capped so low that the only doors we could pick were the Hole, Befallen and one of the gates in Najena. With my rogue skills capped, so far my bard hasn't found a trap or lock I couldn't solve within a couple tries and it's very rare that I set off a trap doing so (and even if I do, I keep my cure disease/poison song on myself to quickly mitigate most trap effects).