World's Hottest Bats - This company separates itself from other competitors because of the process they use to roll the bats.
When they are rolling a bat, they take the pressure they'd like to end up at, divide that number by four, and start there. For each of the subsequent three cycles, they increase that number by another 25%. Some rollers maximize the pressure on the first sequence, and this causes issues with durability or paint cracking. This more protracted process of gradually increasing the pressure by 25% is my preferred option should I ever roll a bat.
Longballbats.com - If you are a member of any youth baseball Facebook groups, you've probably seen ads for this company. A friend of mine used them for his son's bat and said the process was extremely smooth. He thinks it has made a difference in the bat, but without official measurements, it's hard to tell.
Bigdogbatrolling.com - This company has been around since 2006 and offers many different baseball-related services from batt rolling to glove steaming.
Clubrollers.com - One of the more affordable bat-rolling services available.