The Rogue focuses on stealth and uses it constantly in combat as a means to his high-damage melee attacks.

Stealth, or 'hiding in shadows', is a core ability associated with rogues. In some games, rogues can enter stealth at any time. In others, their ability to enter stealth is dependant on not having gained the attention of any mobs, or on the presence of sufficient shadows to hide in. It is unknown how Vanguard will use stealth - whether it will be an ability, a stance, or some other skill. For Rogues, attacking from stealth will not cause you to break out of stealth if you do not recieve aggro for the attack. This allows vital combos and attacks to take place.

Because their capacity for damage increases the longer they remain hidden, you may see rogues habitually enter stealth mode at the start of a fight and not spring into action until halfway through, when they unleash a devastating sneak attack with a massive backstab multiplier due to the duration of their stealth (this is known as stalking). Stalking gives a rogue accuracy bonuses, which allows them to do more damage.

Rogues will also have an uncanny knack for spotting the weakness of an enemy and exploiting it. Rogues seeking to develop this ability to the fullest can focus on increasing their intelligence stat. The Rogue can also perform traditional thiefly feats such as picking locks and detecting and disarming traps.Sigil has said that, for the time being at least, rogues cannot pick pockets.

Stealth and cunning are the skills of the rogue.

Stealth, or 'hiding in shadows', is a core ability associated with rogues. In some games, rogues can enter stealth at any time. In others, their ability to enter stealth is dependant on not having gained the attention of any mobs, or on the presence of sufficient shadows to hide in. It is unknown how Vanguard will use stealth - whether it will be an ability, a stance, or some other skill.

Because their capacity for damage increases the longer they remain hidden, you may see rogues habitually enter stealth mode at the start of a fight and not spring into action until halfway through, when they unleash a devastating sneak attack with a massive backstab multiplier due to the duration of their stealth.

Rogues will also have an uncanny knack for spotting the weakness of an enemy and exploiting it. Rogues seeking to develop this ability to the fullest can focus on increasing their intelligence stat. The Rogue can also perform traditional thiefly feats such as picking locks and detecting and disarming traps. Sigil have said that, for the time being at least, rogues cannot pick pockets.

Build up critical hit points and exploit them using your assassinate attack. Multiple Rogues can work together to build points faster
Lower the number of opponents that your group has to fight by incapacitating one or more before combat even starts
There is an interesting write up about Rogues in Vanguard over at The SafeHouse. This interview with Darrin McPherson (the class designer) talks about rogues stealth fighting capabilities and potential. He mentions that Sigil wants rogues to require more skill to play than other classes. "It will take a higher level of class knowledge and skill to fully utilize the capabilities of the Rogue.” Also there is speculation of future rogue abilities, as well as some small information of rogue tools.