Cover a 38cm x 33cm baking sheet (approximate size) with cling film, brush with half the olive oil, and spread the mashed potatoes onto the sheet in a 2cm layer. Set aside.
In a medium bowl, mix the fish, avocado, onion, coriander, chopped pepper, ginger, lime juice, and remaining olive oil. Season with salt and pepper and allow to rest for 15 minutes. Drain, discarding any liquid, and spread over the mashed potatoes, leaving a 3cm border on all sides. Lift up the cling film on one side and roll up carefully.
Transfer the roll to a serving platter, and garnish the top with the avocado and hardboiled egg. Serve with the sweet potatoes and corn as side dishes.