You can only do about 20 pounds of chicken in one roaster, and you will need at least 3.
For general procedure on large chicken breast prep, see the orange dijon wedding chicken on the big pots page. Chicken Marsala, requires that you pound the breasts into cutlets before browning, so allow extra time.
Once you are in the hold mode, you set the roasters at 180.
If cooking ahead and reheating: The chicken in a sauce is a good choice for reheating without drying out. Make sure it is just barely brought to 160 degrees internal when cooked, so it will not overcook when reheated. Or cook the day of to 160 internal temp and keep covered above 140 internal temp in the ovens.
See these threads: