Let's take a look at the front roller
Before we dig into the front roller I've got to tell you that I'm surprised by how poorly this roller idles. What I mean is when you have the belt off and you spin the roller it grinds to a stop after about two rotations. I suspect that I know why this is, but we'll know for sure in just a few seconds.
I stopped by Harbor Freight and picked-up a set of snap ring pliers. They have a belt sander on sale for $20! Why am I going through this learning curve with a $200+ sander? Because that's the way I roll, that's why.