Does your strength modifier add to your sneak attack damage? For instance, with a strength of 12 (bonus of +1), would a level 4 rogue sneak attack 2d6+2?
But your STR damage is still in there... if you are weilding a short sword, with 12 STR, and get one sneask attack at 3rd level, you would do 1d6+1 (sword & STR) + 2d6 (SA) damage.
You see, a lot of newer players mistake Sneak Attack for a special attack all on its own. It sounds like that's the case. Allow me to explain briefly.
"Sneak Attack" isn't an attack- rather, it's just bonus damage. Whenever you attack someone under the right conditions, your attack gets a certain amount of extra damage to it (in addition to whatever damage the weapon already did). So if you get two attacks a round, and both of them are under the right conditions, they are counted as "sneak attacks" and gain the bonus damage to each attack. Thus, your Strength bonus is added to the attack, because it's a normal attack- the Sneak Attack damage is just added onto that.
As for the "right conditions", I don't feel like going into it. There's a lengthy article on www.wizards.com if you wanna go read it.