How is the 81-098 Pella roller attached?

Hello! You are correct, the 81-098 roller isn't held in by any fasteners. Instead, it's kept in place with the weight of the door itself. Once the door is out  of the frame and the adjustment screw is removed, you should be able to pull the roller out fairly easily. I've known some service people to use a pair of needle nose pliers.

We also have a guide that you may find helpful. I'll share it below for your review. In this guide, Pella recommend using a wire loop and hammer to leverage the roller out of the frame. You may find this to be easier.

Guide: How to replace the pre-701 and 701 Pella patio door roller

When you turn the screw enough, it should come out. If not, you can always try turning it in just enough so it doesn't stick out and damage the rail. 

For the wire, the goal is to try to loop it around the screw itself. That should provide enough leverage to allow you to pull it out with the claw hammer.

Hello! That's a good question. The only major difference between the two products is that the 81-098 is a genuine Pella brand product while the 81-249 is a generic. We find that both products work well, though there are some cases where the generic roller can rub against the door track, as it sits slightly lower in the frame. That said this is an uncommon experience, and the 82-249 is still a strong option.

Both the 81-098 or 81-249 have a metal wheel. At this time, neither have a nylon wheel option.