Jaroth is the leader of the Eclipse mercenaries at Omega, who shipped tainted element zero across Citadel space. He makes an alliance with Tarak and Garm to take down the vigilante Archangel. Jaroth himself holds a personal grudge against Archangel, who in the last month killed his brother when raiding one of the Eclipse transports. He suggests that when the freelancers are killed he will send LOKI Mechs to take down Archangel. The next part of the plan was for Eclipse, the Blue Suns and the Blood Pack to overthrow Aria. Despite being Eclipse he's not wearing the standard Eclipse uniform, much like Captain Wasea.
Jaroth will become hostile once Commander Shepard helps Archangel and will lead a group of mercenaries in an attempt to overrun them. He is killed, but not before deploying a YMIR Mech, which Shepard has the option to sabotage beforehand.
Jaroth possesses strong shielding and armor, and has moderate health.
Provided you sabotaged the YMIR Mech, then the fight with Jaroth is not that difficult, as the Mech will distract him, dealing significant damage and potentially even killing him for you. If the Mech was not sabotaged, use abilities such as Overload or Disruptor Ammo on his shields, followed by a headshot or two with a Sniper Rifle or Heavy Pistol to finish him off.