Good choice on the Rotella. Either oil is a good choice, but I find the Rotella to be a little cheaper at least around here. UOAs (used oil analysis) show that the 4.0 turns in lower wear numbers with a 40 weight oil. Some of the best UOAs have been from Rotella T6 5w40 and Mobil 1 Turbo Diesel Truck. Heavy duty engine oils seem to do best in the 4.0. Rotella also makes a T5 10w30 semi-synthetic HDEO for those of you who want to stick with a 10w30.
Being in a climate that gets colder during winter I find that a 5w40 synthetic is perfect for year round use. My 4.0 even seems a little quieter. My mpg was unchanged when switching to a HDEO.
With our motors, its important to have a good anti-drainback valve. A Wix or Napa gold filter is fine, Mobil 1, K&N, Purolator, Motorcraft and other good brands will work well. Avoid Fram filters.
