Hi, Rose. Those are pretty big roasters. I cook double hens all the time, but more in the 3-or-less pound range for protein snacks and barbecue packets. It doesn't take twice as long, but just make sure the internal temp reaches 180 degrees (in the deepest part of the thigh). You could probably go at least 2 1/2 hours at 350 degrees for 7-pounders. Also, if you stick a toothpick in a thigh and the juice runs clear (not pink), that's a pretty good indication that they're done.