yes, searing the meat will make it more difficult to roll because the meat tightens up when cooked, and it will also cause it to be more dry because you're cutting it after it's partially cooked, thus releasing juices (aka blood or intracellular fluids) in the outer layer that has cooked.
however, it might be a neat experiment. a loin is pretty lean, though, so there's not much room for error it would be better for a sirloin end roast.
in nomine patri, et fili, et spiritus sancti.
beidh ar la linn.
wisdom is often in short supply within ones' ego.