If your goal is to have 1 of each class at 80, there is little to no need why you should leave the rogue out. Any content to 80 can be cleared easy with just 4 toons. So basically have the rogue following and don't do anything with him (auto attack at best). As you progress and get familiar with your software/macros you can still make him do something.. Just let the rogue leach

Of course if you want to do heroics at lvl 85 with that team, there are more viable ones. But then you can still swap in one of your toons you currently have at 80.

Really there is zero need that you should go for another class and do the whole leveling again later for just 1 rogue, seeing how easy all leveling content is (both dungeons and quests).