I have a roof rack, a hitch rack, a trunk rack, and a bed mounting thing as well (we have a lot of vehicles). Of all of them, the hitch is the easiest. It is supposed to hold four bikes, but we are never comfortable with putting more than two and a kid bike on it, as my husband is very tall and has big guy bikes. So we usually put two on the hitch, two on the roof. I am 5'5 and can't get my bike on the roof of the Sequoia...but I can get it on the roof of my mini...which is my next roof rack purchase (I tested out whether I could get it up there)...I use a trunk rack on the mini at the moment, but it gives me the willies. It is secure as houses, but too much room for human error for me. I always think "DID I strap that thing down?"
FWIW, I can fit a bike in my mini cooper....but nothing else!