I have a yearning for yams (OK, red sweet potatoes) and, believe it or not, have never made them mashed, just baked or steamed. I've looked at zillions of recipes and the closest to make-ahead I've come is "may be prepared two hours in advance". What happens if you make them a lot earlier and reheat?
I was going to peel and cube them, roast till tender, put through the ricer and add butter, maybe a little 1/2-1/2, and seasonings. Does the texture go funky if you let them sit like that all day and then pop the casserole in the oven?