cooking meat and dairy in my oven

Question

1. Am I allowed to cook for example a lasagna and a roast beef in the same oven at the same time? 2. Does it make a difference if the twon pans are covered? I tried to figure this out from other questions and the pages on the laws, but I just don't have the head to figure it out myself. I am sorry to ask a question that was probably answered elsewhere already. Thank you for this website. I had my son make it my homepage.