Okay, okay, so you all know walking makes less noise than running in the game; however, sometimes you just need that extra speed running to get up close to enemies.
Rolling makes your character move at the same speed as running, but at a greatly reduced noise (compared to running). It's not completely quiet as crab walking, but it is not as loud as running across crickety floorboards. The best part: your assassin can change directions while rolling, so roll like Link if you need speed and stealth.
Hint - Bossploitation
The last two bosses on Mission 50 are tough, but easily fooled. Once you find where the first of two bosses are (in the palace cut-scene), head east, towards the river.
The first boss will come down the stairs and approach your assassin. With luck, he will step off into the water and die. If not, push him off (easy) with a few sword blows). The second boss is killed in a similar manner.