I dry age every roast I cook, but I never buy frozen meat so I don't know how that will affect the process. Just make sure your fridge is at 38-40 degrees and the beef is completely uncovered and on a rack. Don't concern yourself with trimming off the dried meat as you age it, you'll just end up cutting off half the roast before all is said and done, and it doesn't drastically affect the process. In my experience you can age a roast that size anywhere from 5-8 days in your fridge and it should be fine.
It will be delicious provided you cook it correctly. My favorite: basic salt and pepper rub, baste in its own juices and about a cup of any red wine. Cook at 275 until it hits 130 on the inside, then crank it to 400 to develop a nice crust and the beef JUST approaches 133-134, or about 5 minutes.
Good luck.
