You can get rollers with and without bearings, BUT home garage doors don't run more than 250 pounds or so, and the shafts on the rollers are hollow, and not that strong. They're designed to support the door against wind loads (which is easily way more than the weight of the door), but not much more.
Are your rollers plastic or metal. The plastic ones I've seen don't have bearings, and are popular to lessen the noise of the door that's transmitted to the house.
Maybe you could look for track and rollers designed for wind loaded doors in hurricane prone areas like Florida, but I suspect it isn't going to be much stronger.