I got to level 20 and it seemed very gear progressive from there and the auction house made nodifference.

I am wondering what the reroll function of the character is and does that provide any benefits??

also I cant find a search function for these questions and google wasn't much help.

if you reroll your character you can choose your class again and start at lvl 1.
After the master quest your char is rerolled as well.
you keep all gear and all profs.

usually you dont reroll in between a climb.. if you need to start again from lvl 1 you can also take another char and switch to your prefered char at the given lvl