One of the most searched areas in bat rolling is how to build a bat rolling machine.
There are several factors that go into building a bat roller.
I will break this article out so you can make a n enlightened decision to whether you want to take on such an endeavor.
Here are some questions that need to be answered before you start a project.

1. How the machine works
2. Parts and Materials
3. Cost
4. Time

How the Machine Works: Before any of these can be answered you will first need to decide on what type of a machine you are looking at.

1. Perpendicular
   1. The bat is inserted 90 degrees to the rollers and can only roll 1 way.
      
2. Parallel
   1. The bat is inserted from the sides along the plane of the rollers and the entire sweet spot can be rolled at once.
      

Most parallel machines can roll both ways, but a perpendicular machine can only roll 1.
Also a perpendicular machine will leave flat spots in the bat and not roll the entire sweet spot.
We highly recommend a parallel machine.
The machines work by compressing the carbon fibers and laminates between rollers and then rolling the bat between the rollers.
Primarily the sweet spot of the bats are the section you are targeting during the roll.
Material List

1. The Shell
   1. Typically made of steel or aluminum
   2. Holds the guts of the machine
   3. Welded or screwed together
2. Upper Carriage
   1. Holds the upper rollers
   2. Moves up and down
   3. Tolerances are tight
3. Bearings
   1. Rollers Bearings
   2. Thrust Bearings
   3. Bushings
4. Shafts
5. Handles
6. Rollers
   1. Made of plastic, steel, wood, other
   2. Tolerances are very tight
   3. The center hole through the roller must be fairly exact
   4. Rollers are machined on a metal lathe

Cost The cost of building a machine can greatly very...
but you can figure the minimum will be $200 plus, depending on your bearings and roller materials.
It will be more for the state of the art plastics that are being used in the better bat rolling machines.
Time Building a machine will take some time as you will have to draw out the design and then cut and machine the parts and gather the bearings etc.
Bottom line is this is a project that can be taken on if you are a do it yourself person who has proper equipment and time and some designing knowledge.
A machining background or a friend who has one would help here.
Another viable option is to purchase a Bat Rolling Machine directly from a reputable manufacturer.
Here are a few things to look for when choosing that manufacturer.

1. Reputation
2. What type of machines are the offering
3. Do they have multiple models to fit you individual needs
   1. We recommend parallel machines as they give you the best of both worlds and are not limited to partial break in as the perpendicular machines are.
      
4. What plastics are they using in their bat rolling machines

You need to stay away from a plastic called Acetal with a trade name of Delrin.
It is really hard and has zero forgiveness.