By limiting the troops the rogue it paired with; IE if you have 4 different kinds of units and 4 rouges the rouges have a chance of turning into any one of those units. but if you send 1 unit complemented by 7 rogues all the rogues will turn into that unit when hit. Also Alcatraz and rogue hideouts are a very good combo i get 7 free rogues per day for just having the buildings.
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OH! forgot the GvG aspects of the rogue they can be used in ANY era of GvG BC the troop has no set era.