In the hall before you enter the room with the shield door you will see a thing of rocks that you can move. Drag it into the room with the door and to the far wall (this wall rotates when you step on the button). Face your back to the rotateing wall and power-up and kisk the thing of rocks once kick is completely powered. Quickly roll backwards, the wall will rotate rather quickly so you don't have time to run there. Once on the other side you will fight several undead. There is a ladder in this "secret" room, climb it. You can now climb across a beam to retreave the sheild.

here's how i did it, and you don't have to power up, tho it might take a few tries. with your back to the rotating wall move the rocks slowly (don't kick the rocks). youre gonna try to put them on the very edge of the button. once you see the button start to go down, you'll have a second or two (if that) before the wall rotates. once you get the rocks on the very edge of the button, once you see the button start to go down let go immediately, run a bit towards the wall and push R1 (the rush attack) which will send you foward fast enough to pass the wall.