Like Wayne says. The "dry" tongue weight is not what you need to be concerned with, it's the loaded tongue weight.
The "dry" tongue weight of the Roo 23SS is listed at 435 pounds. As you can see my measured tongue weight is about 675 pounds and Wayne's is at least 600.
The Rockwood 2604 specs at just over 6600 pounds fully loaded so the truck should handle it nicely albeit not as easily as the Roo 23SS. Tongue weight should remain under 900 (my guess!).
I can't imagine, though, that your F150 will be rated any less than my Expedition's 900 pound tongue weight limit (with a WDH).
-- Chuck