I called in two bucks during rifle season this year using the buck roar. One was a 2.5 year old seven pointer and the other is dead (see pic below). Both times i did a calling sequence that included a few bleats, soft grunt, and eventually the full blown buck roar as aggressive and loud as i could get.
The seven pointer came in within 1 minute. He was very alert and and looking for the source of the noise. He came from a bedding area and cirlced directly downwind from me, 20yds from my stand,before he realized something wasnt right and went back where he came from. The buck exited a known bedding area and then took a path that ive never seen deer use, just so he could get downwind.
the second buck came in from a staging area off of a food plot. I specifically heard the roar coming from the area he was at two nights prior two me killing him. It was the most awesome sound i've heard in the wild. If anyone has watched the video, the scene from the property in illinois that someone sent in is the exact sound i heard at least 3 times. If i could describe the sound I would call it a roar. I could also hear bucks fighting in that area several times that week. This buck responded in less than 5 minutes coming from downwind and again was very alert and seemed to be searching for the noise. I think the only reason he didnt wind me was because i was 30" off the ground. I shot him at 15 yards.
I think the roar is best used in a sequence of calls (as with any other call). I try to imitate an actual event just as if the deer are there with me.