Narration gives a rather nasty Stealth penalty. I mean, if you're saying what's happening while you're trying to be sneaky, people are likely to hear. Just sayin' :-)
Joking aside, describing something like this isn't truly that hard. Unless the rogue's trying to be stealthy, nothing needs to be said on the matter. When he's trying to use the skill, it's time to be descriptive.
"You slip into the shadows of the wall and work your way toward the end of the alley. A rat scurries by your foot and doesn't even notice you as it searches for its next meal."
"You hear baby birds chirping on the branch above you as you slowly position yourself on your own branch, waiting to take the shot that will put down the villain's bodyguard."
"One moment, the guards eye your party warily. The next, you hear a guard say 'wasn't there another one with them?' They blinked; you were lost to sight between one second and the next, one moment a little to the fighter's right, the next...?"
Other skills can be described in various ways. For Knowledge skills, make up some references to obscure tomes. For a Craft skill, talk about the steady hands and pace of the maker. For Perception, eagle eyes, the nose of a fox, ears to match. Refer to things that the players can easily relate to and grasp.