In a large bowl, whisk together the flour, cornmeal, salt, sugar, baking powder, furikake, and dried ginger.
In a second bowl, whisk together eggs, milk, and sriracha until combined. Pour wet mixture into the dry mixture, and continue whisking until a batter has formed.
Heat oil in a heavy-bottomed Dutch oven or electric deep fryer to 350°F.
Take an uncut spicy tuna roll and dip it in the batter, making sure to coat it evenly; brush off excess batter with a pastry brush. Using a pair of tongs, carefully place battered sushi roll into the oil and fry for about 90 seconds, or until the batter is just cooked but the sushi inside is still raw. Remove from the oil, and place on a paper-towel-lined plate to drain. When the roll is cool enough, insert a large wooden stick or a pair of chopsticks into the center of the roll.
Serve with sriracha mayo, hot mustard, wasabi, and/or pickled ginger.