Young Writers Society

Ok, here I am going to explain in more detail all the roles available within the Sith Empire.

The Warriors
Warriors focus more on their lightsaber combat than their use of the force, making them effective at close-quarters fighting.
The marauder takes this a step further, entering a force-induced battle rage and throwing themselves into combat. Marauders will frequently use two lightsabers to make them that bit more efficient.
Juggernauts utilise cybernetic implants, which allow them to jump higher, run faster, and strike harder than ordinary troops. They are often heavily armoured, absorbing blows that would kill any ordinary person. Juggernauts frequently use their immense stamina to simply overwhelm an opponent, beating them until they are so exhausted they cannot fight, at which point the juggernaut will strike.

The Inquisitorium
Inquisitors train themselves in the arts of the dark side, becoming potent force-users. They often function on the edge of the combat area, protecting the Sith within while striking at the Jedi.
Assassins hone certain force abilities, allowing them great stealth and precision. They use this to infiltrate the ranks of the enemy and strike without warning. A common tactic of assassins is to drain the life force of their targets before attacking, giving them an advantage before the fight has begun.
Alchemists are capable of a wide variety of dark arts, such as the creation of mutant dark-side creatures, and the concoction of explosives and poisons to use in battle, making their skills an invaluable addition to the Sith.

The Army
The Army is constructed of those loyal to the Empire, but who do not have the skill in the force. Sith troopers are experts with a variety of weapons, including blasters, explosives and hand-to-hand combat. Heavily armed and armoured, Sith troopers are capable of tackling all but the most powerful of foes.
Guards are specially trained in close quarters fighting techniques. They utilise heavy armour and weapons such as force pikes and vibroblades to carry out their primary objective: defence. This could be guarding an installation, injured troops, or Sith Inquisitors using battle meditation or similar force techniques.
Sith scientists assist the alchemists in their work, as well as creating a wide range of explosives and machinery to aid the Sith in battle. In combat, scientists also serve as engineers and medics wherever required, and are frequently trained to pilot the craft they service.

If you have any other questions, PM me about them or check on wookieepedia.