In a medium skillet heat 2 teaspoons of the oil over medium heat. Add bell pepper and onion; cook and stir 3 to 5 minutes or until softened. Remove skillet from heat and set aside.
In a large bowl combine crabmeat, panko, mayonnaise, cheese, egg, seasoning and lemon juice. Add onion mixture, and salt and pepper to taste; mix well.
Divide into 10 equal portions; form 2 1/2-inch patties, 1/2-inch thick. Cover and refrigerate 30 minutes.
In a large, deep skillet heat remaining 1/2 cup oil. Add crab patties in batches; cook 2 to 3 minutes per side or until golden brown. Transfer to a cooling rack lined with paper towels.
Place arugula on the bottom of each roll. Top with 1 crab cake and horseradish sauce if desired.
