Patio screen door rollers

What you're showing here is only one component of the larger roller assembly. You very likely have an L style screen door roller, such as our 84-026 or 84-073, to name two random examples. 

In order to narrow down the list of possibilities, you need to remove the entire assembly, L corner and all. This will require partial disassembly of the frame. This can be difficult, so if you're not familiar with how to do this kind of project then you'll need to hire someone to do it for you.

Once it's removed, show us a photo and provide precise, written dimensions of the L bracket. We can then check our inventory for a match.

I know it's a hassle, but there's no other way to identify one of these. Full removal is a mandatory first step.