The input delay in ER is real. I noticed it almost straight away. shield parries are harder and more unreliable than they ever were for me. Sometimes I press the button, I know I timed right, but the input doesn't confirm. It might also help I played Demon's Souls on PS5 as well, it reacts better.
found this: a 60fps video with controller overlay on PC
if I go frame by frame in the video player, I count either 4 or 5 frames of delay (hard to actually make out since the animation into the roll is very smooth)
in a 60fps video a 4 frame delay would be 66ms of lag (that is WAY below most PS5 games btw which are usually above 90ms for regular inputs)
with 5 frames of delay it would be 83ms of delay for the roll, so still very much normal for any game
the right stick movement gets registered within about 2 frames maybe even only 1 (being PC that would make sense) so we have ~33ms of lag on PC on normal inputs, that is REALLY LOW and about 66ms to 83ms which is still below almost any PS5 game.
again, you have to measure from the moment you let go
edit: going by the fastest button press in the other video for DS3 I linked we got 2-3 frames delay on that for letting go of the button, but that is a 30fps video so that would be either 66.6ms or 99.9ms
it seems therefore either to be identical or that AT MOST you have maybe a single 16.6ms frame longer delay in Elden Ring. maybe even the PS5 version in particular being at fault? that wouldn't be the first time one version of a game has weirdly more latency than the other. the PS4 version of Prey comes to mind compared to the Xbox One version. or the PS4 version of the Mega Man X collection which also had REALLY high latency compared to Xbox One