I am looking to buy a road bike (specifically the one linked below) I am trying to figure out the sizing. So the road bike I am looking to buy is 21.5" and I am 5'11 so my bike height range should be anywhere between 56cm-60cm. This bike would technically be a little below my recommended ride height. Again this is going to sound really dumb, but couldn't I just raise the seat to make it the height that suites me best? Maybe road bikes are more involved than just the seat maybe the handle bar height is too small? No clue this is why I am posting this because I need good advice before I spend the money. Please and thank you very much!

https://tallahassee.craigslist.org/bik/5017445800.html