It can actually reduce the risk of ordering the incorrect roller conveyor and not having the correct part available when equipments break down. There are some general do’s and don’ts when you are ready to place the order for replacing the roller conveyor:

Do’s

When you are preparing for ordering take a note of make, model and serial number of the rollers you need and the corresponding conveyor. If the conveyor is custom made, having the serial number will identify the special component that would be needed.
There are terms such as snub roller, which depending on the model of conveyor may have different part number based on where is the roller position. So always provide the description that where the roller is used else you may end up getting wrong part. Like 2.5” diameter snub roller has a different part number than the 2.5” diameter snub roller used with an 8” diameter pulley. So based on its position the part is defined.
Don’t

Never overlook the details like roller diameter and roller length. There are multiple roller part number for rollers in the approximate 2” diameter range. Some part numbers can be used in place of one another, but we want to replace the rollers with the rollers of same specification we have to be careful.
A 2” diameter x 12 gauge conveyor roller is often mistaken for the 1.9” diameter roller. To avoid such mistake use precision measurement tool, a pair of caliper, to measure the exact diameter.
By keeping in mind and considering the above points you can avoid the mistake of ending up with wrong sized part of the conveyor roller. But sometimes you can take the help of the technical person from roller conveyor supplier who arrives from the company and he can provide you with right information.