just so your clear on why its important to have the proper tool......what you need for a roll cage tubing bender is a "mandrel tubing bender". Mandrel benders pull the tube around the radius thus preventing the tubing from crushing. benders that push the die into the tube like the greenlee and cheap copies will crush the tube or even kink it. you can not use that rolling type tube bender for roll cages especially main hoops due to tight bends needed, and that bender in eastwood will not handle roll cage grade tubing. that thing is only good for light tubing. and a roller type bender has to go back and forth several times to get the final bend so it would be hard to duplicate bends over and over. look at vansant and they should have manual mandrel benders for about 500 or so. Check out the links below. tubeshark is a professional model the jd2 is an affordable model that is perfect for the home shop. and good price too! hope ive steered you in the right direction.
http://www.tubeshark.com/
http://www.jd2.com/
Marc