I was wondering the same thing. I plan on taking 5 balls with me - a 3-ball roller with 2 balls and some clothes (trying to avoid the fee of $50 each way for overweight baggage, but that's another rant ;-) ), a small suitcase with 1 bowling ball in it, and a 2 ball tote I want to carry on.
I looked on the TSA website, and bowling balls were not listed under sporting equipment that you are not allowed to carry on, so I'm guessing it is OK. Please post if you hear otherwise, I leave tomorrow.