It sounds like the only thing you really need to be concerned about with the vehicle being picked up is that it can roll on its own. You may want to consider bringing a set (or at least a pair) of rollers that you know hold air for sure. You mentioned a winch. Are we talking about a full blown winch mounted to the trailer or is it a come-a-long? If the latter, I would really suggest bringing a good set of wheels/tires. Again, taking into consideration it needing to be a roller, and if the brakes are stuck, I may consider items such as a dead blow hammer/rubber mallet, some pry bars and a wisk broom to clean out all the crap that likes to lodge in between drums and internals.
I am assuming you all ready have your tie-downs but you may want to add duct tape, bailing wire, a jack, a jackstand, a star bar and bring a AAA card as well. Extra money, a good credit card, a cell phone, flash light (w/good batteries), first aid kit and food (cooler with cold drinks and ice) make the trip a little more comfortable.
It wouldn't be a bad idea to give the tow vehicle a thorough going over and replace any questionable hoses/belts, etc. and make sure that all of the fluids have been checked and are good to go. Bringing extra fluids (oil, trans, brake, coolant, etc.), fix-a-flat and a tire plug kit may not be a bad idea either.
That's it for me but I am sure others will chime in with other important items to consider.
