Place 16 overlapping slices of crustless white bread on a piece of plastic wrap and flatten them with a rolling pin.
Heat the olive oil in a saucepan over medium heat and cook the onions and garlic until translucent. Add the chili powder and sugar and let simmer. Stir in the soy sauce and balsamic vinegar. Add the ketchup and cook for 5 minutes while stirring. Season with salt and puree the sauce for a smooth consistency.
Add 3-4 tbsp of the chipotle sauce to a bowl and add cream cheese and mayonnaise. Season with salt and pepper and mix everything together.
Spread ⅓ of the cream over the bread.
Dice the tomatoes, red onions, and jalapeños. Add them to a bowl with the peas, corn, and tuna and mix well.
Spread the tuna mixture over the cream-covered bread, leaving a 1-inch free margin along the edges, and use the plastic wrap to help you roll it up.
Place another 16 overlapping slices of crustless white bread on the edge of the tuna bread roll and roll them flat. Coat the bread with another ⅓ of the cream and the rest of the tuna mixture, and roll up the entire thing. Refrigerate the tuna bread roll for at least 2 hours.
Pour the remaining cream into a piping bag and garnish the roll with it, along with cherry tomatoes, green olives, and fresh parsley.