I get this question a lot. There are different opinions on the subject, but to me, the answer is your bat will NOT loose any durability, but may actually last longer if rolled correctly. Before I go on and elaborate, i will answer a misconception and 100% bogus claim made by other bat doctor websites.
"How can bat rolling not loose durability when you are simulating hits on the bat before i even get the bat?"
Any company claiming a fixed number of swings rolling simulates is making up a number to make you feel like their process works. There is no science and measurements behind anyone making this claim. They assume because they are breaking down the fibers of your bat its "like" hitting a ball 500 times. 500 swings is a made up number to make you feel warm and fuzzy about their process. Any seasoned bat doctor has no more inside information than the other. What they do have is the propensity to spew BS to the public leading them on to believe they know what they are doing
If rolling really did remove 500 swings from your bat, bats would break left and right all day every day because bats these days are designed to break so you go and buy another. I can tell you some bats dont even last 500 swings stock so how can rolling remove 500 swings and you still have some use of the bat? Competitors can post up all the bar graphs they want and fictitious studies and random encounters with Ph.Ds on philosophical discussions on the subject. I have a masters degree in Business Economics with a minor in Finance and i can wow you with excel charts and fictitious numbers as well, not to mention all the discussions i have with my old professors on bat rolling and shaving at alumini events. Its all BS. Don't believe any of it.
The truth to the question is found in a very simple comparison of reality. Lets take a comparison of 2 test samples
Test sample 1 -- a rolled bat. Bat rolling can evenly break in your bat, if done correctly. I stress if done correctly because you can find people with bat rollers everywhere, but not many really know how to properly roll a bat. Its very easy to over roll or under roll a bat. Rolling is more of an art vs a science and takes years of experience and countless bats to hone the craft. Point being, if done how it should, your bat will be evenly broken in.
Test sample 2 -- Take into consideration the average person who bought a bat off the shelf and simply peeled it out the wrapper. One sure fire way bats break prematurely is because the barrel is not evenly broken in all the way around the barrel or are constantly pounded on 1 side. I have played baseball and softball my entire life and know my tendencies as well as others. Most people when they purchase a bat just go out and start hacking giving no consideration to rotating the barrel every time they get up to the plate. Most people also like to line up the decals a certain way because of the visual they see on the bat. This is how bats break prematurely because the bat does not break in evenly. We service used bats everyday and most always see spider cracks on one side of the barrel or when we put the bat through the roller, 1 side is much softer than the other. These are clues into how the bat has been used up to when it was mailed in. Granted not all bat owners do this, but i would venture to say the vast majority of the softball and baseball community hit bats in this fashion.
Conclusion -- Taking into consideration the life span of a bat hit by the average user vs a bat that has been professionally rolled, i will bet you the rolled bat will out last the other bat used in this fashion all other factors equal. I have a blog on "How long will my bat last?" to where i go into depth on what factors effect durability. Knowing the nature of the materials you work on and applying logic based principles, even wall flex is the key to not only getting consistent performance from your bat, but also help reducing the chance of a bat breaking prematurely. There is no magic number rolling simulates and remember, bat rolling adds 0ft of distance to your bat. If you see anyone advertising distance gains on a rolled bat, they are not living in reality. Rolling is a break in service to your composite bat. Rolling does not alter the structure or internal make up of your bat in any shape or form nor does rolling create any additional trampoline of your bat than what it would if you broke it in evenly on your own.
In my professional opinion, bat rolling done correctly is not detrimental to the life span of your bat, but can actually help make the bat last longer. All the bats i swing myself, I heat roll because i know it works and know my bat will hit consistently no matter how i square it up to the plate.