I'm having a real problem with the finger rolling aspect of sweeping. The problem is, my third ring finger won't bend 'backwards' at the first joint or the second. I've watched videos and read a few lessons and most of the time the guitarists ring finger is flexible and mine just won't bend or arch like my index. I can't get it anything more than completely straight. Does anyone know what I mean? I don't know if this is normal or not, but the people I've seen don't have this problem.

Years ago when I was learning major "barre chords" on the 5th string I was told that some people can barre the three strings with the ring finger because it bends backwards (as opposed to three fingers) and some can't and that's just the way it is?

Does anyone know what I'm talking about? I don't know if this is common or not, but it sure seems to make sweeping hard and uncomfortable..
just practice slowly bending your finger down, it'll seem really awkward for a while before you get used to it.

unless you meant you've already tried this and it wont bend at all, idk
It just won't bend. I have no idea why. It won't bend it even if I forced it, I think it would break lol. Like trying to bend your arm at the elbow in the other direction. Is this abnormal then?
TS, you might just wanna "home in" on those two strings which require the roll.

I'll assume you're practicing the "A" shapes (more specifically the A minor shape) starting on the 5th string? So the D and G string yes?

Forget about the whole arp, just isolate those two strings. Your 3rd finger does not require to bend "backwards", just "dead straight" is enough.

Just practice going bak and forth on those two strings. SLOWLY. It'll come mate.