If using frozen redfish fillet, thaw completely in the refrigerator (4-8 hours) or at room temperature (1-2 hours). Pat dry with paper towels.
Clean the bell peppers, remove seeds and stems, and cut into approximately 1 cm × 1 cm pieces.
Peel the garlic cloves.
Pat the redfish fillet dry with paper towels. Cut into pieces approximately 5 cm wide. Season with salt and pepper.
Roll the fish pieces in flour, coating all sides evenly.
Heat the olive oil in a large pan over medium heat. Add the rosemary sprig, thyme sprig, sage leaves, garlic cloves, and chili peppers.
Heat until the garlic is lightly browned, about 5-8 minutes. Watch carefully so the garlic does not turn dark (it will become bitter if overcooked). Remove the garlic, herbs, and chili peppers with a slotted spoon and set aside.
Increase heat to medium-high. Fry the floured fish pieces in batches (do not overcrowd the pan), turning once, until golden brown on both sides, about 4-6 minutes per batch. Remove cooked fish with a slotted spoon and set aside.
Add the bell pepper pieces to the hot oil and cook for 3-4 minutes, stirring occasionally. The peppers should remain crunchy. Remove with a slotted spoon.
Arrange the fish and peppers on a serving plate. Top with the reserved garlic, herbs, and chili peppers. Serve with lemon wedges on the side, squeezing the juice over the fish just before eating.