A friend of mine tows his seven metre boat from Melbourne to Broome in WA every year for the Sailfish tournament and one year had over 10 blow-outs on the way up. After some advice he removed the tubes from his tyres and had none. The reason for the blow-outs was the expanding hot air in the tyre could not escape. The pressure simply built up till the tubes blew up. Rollers Trailers are fitted with rollers, teflon skid pads, side bearers or a combination of all three.
Rollers come in two categories, side wobble rollers and keel support rollers.
Whatever type you have it is important that they do two things. First and foremost they must roll and secondly they must all support the hull evenly. It is probably because the keel rollers are seized, or the rig is not set up correctly. Such a situation is not acceptable and we should get the trailer fixed so it does work correctly, afterall boating and fishing should be a fun experience and we shouldn't be breaking our backs to launch and retrieve. Rollers which are split, or not round any more must be replaced and if the rig is not set up properly then head down to the local ramp, launch the boat and get the tool box out and adjust it.