In a two deep safety allingment, it is comstumary for one Safety to have a short and long, deep coverage responsability. You can have two safeties responsable for half the field deep but that's normally in a prevent situation, not in a nickle or dime. Everybody does it a little different but bottom line, two critical things went wrong in both coverages. The speed on the field was not recognized and accounted for in coverage, one, and the speed WR was not bumped off the line. Both of these two things are critical. IE, if Roy had deep intermediate responsability, this should have been changed once Moss lined up to his side of the field. Thus, allowing Roy the ability to free up on the short assignment and get right into backpeddle. No excuse, at all, for giving up a free release on Moss. Again, recognition of who is on the field, what the game situation was and what your responsability should be in that situation. IMO, this was probably the biggest error commited. This chuck on the speed guy allows the defense that extra second or so to see where the deep threat is coming from. It's the difference between seeing the steak and getting into position to provide help and getting beat for six.
Everybody is at fault on those two plays. Poor coaching on recognition, responsabiliy and adjustments. Poor execution on behalf of the players for not reading keys and communicating what should be understood between the LBs and DBs.