I have been using 1T of kosher salt for the last several months. For my last batch, we scaled back a bit more to 3/4T.
The lower amount of salt allows me to be a bit heavier on the application. My family likes the heavy garlic flavor, enhanced by the pepper and parsley.
I also apply the rub about an hour before cooking. That gives some time to extract some of the juices from the roast, allowing for a nice crust during the cook.