mac & cheese
I have done both. If frozen, do it at a lower temp for a longer time (ie: 300 degrees for 1 to 1 1/2 hrs). At room temp, can be 350 or 375 degrees for 30 mins or so. (Depending on how deep the M&C is).
Note: You can always broil for a couple minutes at the end if it appears to be cooked through, but not yet golden brown.