How long do you want to hold it?
Got an oven?
Pre heat some bricks @250 for an hour
Place ratty towel in bottom of cooler.
(do not place bricks directly on bottom of cooler. Don't ask me how I know.
)
Cover bricks with another ratty towel.
Place roast in pan covered in foil on top of towel.
Place lid on cooler.
I've kept butts, birds, ribs, etc.
for up to 6 hours this way.
You can even preheat the cooler with HOT water
prior to placing the bricks.