If you're just between figher and mage, then here's what I think @__@
As a fighter, both a tank and a DD, from what I've observed you have to put effort into what you're doing. Especially when you have a party to protect, no one's going to like you if you let aggro get to a mage, or some squishy guy. You also might have to take damage as the front-liner, so if you like front line action and tanking a lot figher might be cool. I personally have never played a fighter, and am not very interested in one because I don't like front-line action too much @_@
As for a mage, if you like doing lots of damage, then a mage would be cool. Personally, I find that this class relies pretty heavily on a party unless it's PvP. I don't have much experience with a mage, because I got pretty bored of it, even compared to my archer. I don't mind dying, it's just when I lag I can't attack and without a supporting party a mage dies really easily @_@ But if you want to deal big damage and have friends you can party with I think mage is cool too.
I agree with Hessah on the trying out both classes thing. If you can't decide, you should at least do the class change with both of them and try them both out. A lot of people say that you don't actually try out a class until your 3x, and some people even say 5x .___. But I think trying up till lvl 25 should be far enough to decide.
I don't really understand what you mean by "re-rolling", but give the archer a try too. I first started playing an archer because the fem archer 1x armour looked cool to me xD I found that while archers are a fairly popular beginning class, they get rarer the higher leveled you go making them more attractive to me 8D