I don't use it regularly but have gotten some from races. It is 35 vs 20mg caffeine, slightly more potassium, and a special "roctane amino acid blend". Can't help you with that last one. No idea. Sodium, calories and carbs are equal. It is okay on my stomach, but tasted a little worse than the usual gu IMO. I've noticed that with other fueling with extra caffeine.
ETA: I was comparing to Salted caramel which already has elevated sodium. Compared to vanilla the Roctane has double the sodium.
I used the salted chocolate roctane at my race on Saturday - bought it at the expo. Agree with above that the taste wasn't as good as regular gu. And they are expensive. Past that it has more caffeine and potassium. I thought it had more sodium too but maybe I'm wrong about that. And then protein. I can't tell you I noticed a difference during the race, but I only took one.
EA: The other gu I used during the race was caramel macchiato. I like that one and will stick with that.