The cooking time on frozen lasagna varies, depending on how thick the lasagna is and what kind of oven you have. A basic lasagna typically has approximately 4 layers of noodle â¦ s, cheeses, and sauce. So, based on that figure, it would take approximately 1 hour at 350 F in a convection oven.In a regular, conventional oven, it would take approximately 1 hour and 15-20 minutes in a preheated 350 oven. basic lasagna typically has approximately 4 layers of noodle â¦ s, cheeses, and sauce. So, based on that figure, it would take approximately 1 hour at 350 F in a convection oven. In a regular, conventional oven, it would take approximately 1 hour and 15-20 minutes in a preheated 350 oven.