Gather all your ingredients and preheat about 2 inches of oil in a frying pan over medium heat until it reaches around 180°C (356°F).
In your large mixing bowl, combine the mashed roasted vegetables with the beaten egg, chopped parsley, smoked paprika, salt, and pepper. Mix everything thoroughly until well integrated and the mixture feels cohesive.
Add the panko breadcrumbs gradually, folding them into the vegetable mixture until it becomes firm enough to shape without sticking excessively. If it's too wet, sprinkle in a bit more breadcrumbs.
Using a tablespoon or your hands, scoop out portions of the mixture and shape them into small, compact ovals or rounds. Place each croquette on a plate as you work.
Carefully lower each croquette into the hot oil, using a spatula if needed. Fry in batches to avoid overcrowding, cooking for about 3-4 minutes per side until they turn golden brown and crispy.
Once golden and crispy, use a slotted spatula to transfer the croquettes onto the paper towel-lined plate to drain excess oil. Let them rest for a minute to set their shape.
Serve your vegetable croquettes hot, with a squeeze of lemon or your favorite dipping sauce. Enjoy the satisfying crunch and tender interior with each bite!