How do I book for longer than 60 minutes for in-home sitter?

There's no way to book sitters on an hourly basis on Rover. I would suggest you search for traveling sitters (drop-ins, walks or even house sitting) and discuss with them via messaging what you are looking for. Then they can tell you if they are interested and how much it would cost, which they would enter on a modified bill for you. You may need to contact quite a few in order to find someone.