Gol D. Roger was not a devil fruit user.
It is the curse of the devil fruit. When they eat the fruit they gain new power and new skills but the cost of this new power means they must lose something like the ability to swim. They have not explained exactly why this happens.
We'd all be pure of heart and go to Heaven.
Admiral Aokiji (Kuzan) uses the Hie Hie no Mi, the ice devil fruit. Admiral Kizaru (Borsalino) has the Pika Pika no Mi, the flash of light devil fruit. Admiral Akainu (Sakazuki) uses the Magu Magu no Mi, the magma devil fruit. All three are logia types. After the timeskip, Akainu has become Fleet Admiral, and Aokiji has resigned. Two new Admirals have replaced them, only one has been revealed, Issho, aka Admiral Fujitori (Purple Tiger) with a gravity-based paramecia devil fruit.
yes you can eat fruit.
Fruit flies eat fruit and so do humans
Wolves and rabbits do not eat fruit. Some insects, such as fruit flies, eat fruit.
They do eat fruit. They eat grapes and raisins.
Macaws eat fruit but not fruit trees.
Jamaican fruit.
Snakes do not eat fruit.
Cassowaries eat fruit!!