, but you're still sitting there for 30-60 minutes in most cases waiting for it to show up.But you aren't sitting! You are doing other things. Spending time with a child, scrolling the internet, watching tv, playing a game, doing housework, and so on.
If you roast a chicken, you still need to prepare it. This takes time. You gotta wait for the oven to heat, and you might need a side. You might need to put them in the oven at different times - that chicken is going to take 1.5 to 2 hours, after all. When everything is said and done, you then need to clean up the mess.
All in all, it will definitely take longer to cook yourself and you could use that time to do other things.
As a sidenote: This seems like a fancy meal. Its been some times since I ate meat or lived in the US, but I remember rotisserie chickens being cheaper than whole chickens from the frozen section at the store. Is it not still that way?