Contact the hotel directly and inquire when room service starts serving breakfast. Usually, it is around 6:00 a.m. However, I have had this same issue (early flight) and arranged to have breakfast delivered earlier... something like 5:30 - 5:45.

If you need to arrange this, talk to the F&B manager a couple of days before to see if it is possible and then remind him/her the day before.

If all else fails, I'm sure you can grab something at MCO.