Cooking rib roast for a large group with minimal time We're having a decent sized party, and hoping to serve rib roasts (we're looking at 3 7-rib roasts).  The problem is, we only have access to the ovens on site 2 hours before we want to eat.  This doesn't give us enough time to do the full cooking on site.  What's the best way to start them at home and finish them off on site?  Would it work out to do a couple hours at 250 or so to warm them, transport them foil wrapped in a cooler, and then blast them at 450 on site?  Or flip that around and cook at high heat first and try and hold them once we get the kitchen?
This is a perfect application for sous vide cooking.  I would pre-sear, bag, sous vide @ 58C (136.5 F) for 5 to 10 hours, then chill. All that can be done ahead of time.  Bring to the site, re-therm for a couple of hours, crank the oven, and finish in a hot oven to develop outer crust.