When Indy kneels and rolls forward to avoid the blade trap, there is a very quick shot an instant later of a forearm putting a piece of rope around a gear and stopping the trap. Whose arm is it? Surely not Indy's. He had just rolled an instant beforehand into a location he had never seen before, and would not be prepared to perform this action, nor even know the rope and gear existed to be stopped.
Whose arm is it? Surely not Indy's.
Yes, it surely was.
Aside from the "kneels before God" turning into a roll, that snippet of the scene was completely plausible.
At the end of the [kneel] roll, Indy's directly facing the rope -- which is hanging on the wall right next to the wooden gear, and with a noose already formed -- and he analyzes it for a split second (Harrison Ford makes an upward gesture with his head to emphasize that he's considering the rope). Then, he takes the rope and stops the gear.
IMO, a near instantaneous connection between the moving metal blades and the moving wooden gear could have easily been made. With Indiana Jones not only being an intelligent person, but also highly experienced with thinking on his feet, performing this feat is well within his wheelhouse of capabilities.