Preheat the oven to 350 F.
Arrange the prepared vegetables on a sheet pan, drizzle with the olive oil, season and stir to combine. Transfer to the preheated oven for about 15 minutes, or until tender, stirring half way through the cooking time. Cool.
Meanwhile, drain the crab meat, carefully remove any shell fragments and reserve in a bowl.
Sprinkle the crab meat with the Old Bay, add the cooled roasted vegetables and gently mix by hand to distribute all ingredients, being careful not to break up the lump meat.
Mix the egg, mayonnaise and Dijon together in a small bowl. Pour half of this mixture over the crab meat. Gently mix to moisten the meat.
Add the bread crumbs and gently mix again. Form a cake and test the consistency. Adjust with more of the mayonnaise mixture as necessary.
Form four equally-sized cakes, sprinkle with additional panko and reserve until ready to bake.
Increase the oven temperature to 400 F. Sprinkle some additional panko on a foil-lined sheet pan, lightly greased with oil, or in the bottom of a greased baking pan. Place the crab cakes on the prepared pan or dish, transfer to the oven and bake or 8-10 minutes, or until golden brown and warmed through.