100 yards is still too close. A gobbler can hear loud yelps from a very long way away. Several hundred yards, in fact. If there are no hens with him, it should be a cinch to call him in. I'd say 200 yards is about as close as I'd want to get to a roost, but 500 wouldn't be too far. You'll make some noise getting your setup just right. In fact, I think I'd find the right spot and make my blind the evening before.
Set a hen decoy up in a hardwood flat with good visibility. Better yet would be some sort of opening. If you have access to one, a jake decoy in addition to the hen would be great. Positioning them around 12 yards from your spot should provide you with a good shot.
You'll want to hide yourself very well, with a big tree to break up your silhouette. You also want to put something in front of you, to hide your movements as you draw. A piece of burlap works well.
Some loud yelps will let the birds know a hen is in the area, and should start them moving to you. You'll know one hears you when he immediately gobbles a response to your yelps. It'll take some time for him to work his way to you, so be patient.
Once he sees your decoy, go very easy on the calling. A quiet cluck or two will be all that's needed. When he gets within 75 yards don't make a peep, unless he hangs up and won't come to you.
Once you see him, you'll want to have your bow up in front of you. If you have a jake decoy, he'll go to that first and put on a show for you. He'll be moving all around and should provide you with a good shot opportunity.
Honestly, you should have some action pretty quickly, but it could take all morning. I shot a bird opening morning at 8am, and had another hunter blow it for me yesterday at 9am (the gobbler had already seen my decoys and was coming in).
An afternoon hunt will be a little different. You likely won't hear gobblers coming in, as they tend to clam up in later in the day. They'll still come in, especially if they haven't found any hens. If they are with the hens, the trick is to get the hens to come to you. It takes a different calling technique, though.
At any rate, good luck. Make sure your up to snuff in the accuracy department and study up on where to hit them. You should be able to nail a tennis ball at 10 yards. If you can't do that regularly, don't feel bad if you need to use your shotgun.
Good luck, and let us know how it turns out. Just by being out there is going to give you a great education. They are a blast to hunt.