A good team will need a balanced roster of soldiers. An air support unit can call in airstrikes unless and EMP tech unit is protecting the area. A drone tech soldier can send a remote controlled mini-chopper to scout ahead and pinpoint enemies for the whole team, but without teammates to protect them they'll get blown away while fiddling with their joysicks. Playing as a sniper, we flew a drone up ahead and from the air it could show us the location of enemy soldiers behind walls and cover with highly visible red diamonds.
In the beginning of the match the roles are less important, but as you accumulate experience by using your abilities and getting kills, your skills will become more powerful. Each role has three tiers of skills, and they get progressively more havoc wreaking (see the level 2 carpet-bombing picture above). We had a good time sending in a mortar shooting drone safely from the sidelines of the fight after we had powered up by scoring sniping kills. The air strike soldier can carpet bomb an area or call in a gunship for several seconds of laser targeted aerial gun blasting, and the ground support units can place powerful stationary guns.