Some of my best hunting has occured after 4:00 p.m. I killed one of my birds this year at 5:20. You can bump birds anytime you enter the woods during the day. I wouldn't try setting up under the roost just yet. You may be able to call in a love sick gobbler before he goes to roost. You may want to set up a couple hundred yards off the roost. That way if the bird doesn't come by you on his way to roost you can slip out without spooking him.