Depends on how low you want to go. I'm 5'9" and chose the 2019 54cm Roubaix over the 56cm after testing riding both because I wanted a more aggressive fit and it definitely felt nimbler. I don't regret it, but taking the smaller size does have some compromises, like needing a longer stem, more weight distributed over the front, and more toe overlap. The 2019 geo is only slightly different from the 2020+ generation's.