Generally, the only reason people do this is to salvage the rims.
And that being said, both of the afromentioned ways (soaking in acetone, or heating in an oven) works - albeit with their inherent consequences.
Any post-production heating or solvent-soaking surely can't be any good to the longterm use of the remaining product.
And I've ruined stuff by doing it both ways - seen rubbers all but dissolve in acetone, and rims turn brittle from soaking all the plastic oils out of them; and seen rims warp from oven heating, and tires turn to goo (even at 200*).
Some folks will swear, and live and die, by one method or another - and it doesn't neccessarily make either one right or wrong.
But my advice would be to see if you can either use 'em as they are, or trade 'em if you can't use the current rims you have the tires mounted to.