Shroomy
Adventurer
Now that you mention it, no, I'm not sure. I wonder if the text would specify if the limit was one reroll, or if there was no limit?
I was reviewing the power in the Compendium and while it doesn't directly specify that you are limited to one re-roll, it seems to me that the RAI was for one re-roll. That's how I would rule it until the power is errata'd.