Reading the rules of Dark Heresy, getting a Righteous Fury rolls a single d10 (for each 10 rolled).
Looking at the rules for Rogue Trader it looks as if a Righteous Fury gives you an entire damage roll (the example is 1d10+2 again.)
The Rogue Trader version looks incredibly powerful, especially when you are using something like a Heavy Bolter (with tearing) where you can be rolling a number of hits already (3d10) and likely to RF at least once during a full-auto attack.
Is the rules difference intentional? Is there something I'm missing? Looking at the Deathwatch quick rules, it looks like it is back to the Dark Heresy method (a single additional die.)