Target-lock onto Rollie and start circling him while he prepares attacks. After he attacks you should be able to get directly behind him while he pauses and circle up to his side. Stand against the tank treads on his side and start hacking away at him. He will not move or try attacking you. You can defeat him in each phase of his battle this way and it requires no minions to do so.
When blue minions are on guard duty, they will rescue fallen peers and drag their half conscious form to you so that you can revive them. However, while not assigned, they will wait for you to micromanage them over to the body by sweeping, making them almost useless in a large battle.
-In order to do this you must have fought Dazzler Beetles (located in the blue minion cave), Puff Beetles (Evernight), Magma Beetles (outside of Heavens Peak) and Battler Beetles. After fighting at least one of each, they will be available at your dungeon. Go to your dungeon and choose to fight one of the four. The easiest way to take out the horde of beetles is to pull only a few from the swarm and take your time killing them individually. Green minions work well sincet they are experts at overwhelming and killing your enemies. Set a marker for them to wait at and they will eventually turn invisible. Pull a few beetles and make them follow you to the marker, where your minions will then jump on them and eventually kill them. Battler Beetles are good for getting Brown souls. Puff Beetles are good for getting Green souls. Magma Beetles give red souls and Dazzler beetles give blue souls. You should get at least 75 souls each time you completely kill all of the beetles that are in the dungeon.
-For fast green minion soul gathering, when you find the green minion hive you will see five green minions jump into the spawning pit for you to take control of. Do not do that. Instead, go to the tower using the gate beside the tree spawn pits to your right, then return to the green minion hive. Five more green minions will jump into the spawn pit and you will still have the ones from before. You can repeat this as many times as desired, but after you take the hive it will no longer work.
While in Evernight-swamp, go near to waterfall with the blue minions. Send them into the waterfall and they will return with gold. Wait a while and send them again. They will return with more gold. You can do this at any time.