Mash the Fish together with the Onion, Green Onion, and cayenne pepper together in a bowl and set aside.
In another Bowl, add the flour, baking powder, sugar, salt and margarine and use your finger to incorporate the margarine into the flour until it comes out crumbly. Add the Egg and mix it with the flour until it's totally absorbed by the flour.
Begin to add the water a little at a time until a workable dough is formed.
Transfer the fish roll dough to a work surface and knead for about 3 to 5 minutes, then cover up the dough and leave it to rest for about 10 minutes.
Roll out the dough to about 1/8th inch thick, then cut it out into small rectangles (this is dependent on how big you want your Fish rolls to be) and you don't need to be perfect while cutting out the rectangles of the Fish Rolls since it's still going to be rolled - no one will see the imperfection.
Take each of the cut-out rectangles and fill it with 1 to 1-1/2Tbsp of Fish then tightly roll the dough and secure the tips a little bit to prevent the fish from spilling into the Oil.
Fry the fish rolls in a preheated oil until it's golden brown.
Serve hot, warm or cold with your favorite drink. Enjoy!