I ran into the same problem. What worked for me was simply restarting the game. The option to reroll then became available on a fresh start up. It greyed out after getting into the game and going back to character select. Try that.
I can see that you just want to streamline the power tab skill switching that happens on the fly during a fight, personally I do that when I realize that I have my pve loadout up when I start pvping. Its the worst cuz my pve skills aren't very good for pvp unless the player is braindead. I usually run away when I find out,…