Wheeling the phalanx

[Tib. Gabinius]

To bring the front in a 90° "Schwenk" (sorry i dont remember the english word right now) to face e.g. an attack in the flanks a greek phalanx or also a macedonian took real long. The romans won the macedonian wars about that fact, cause the mac. formed their battle line to slow and opened their flanks. Also the roman infantery needed time to get into position for that attack the mac. hadnt the chance to rebuild.

If you mean roman formations, which arent same, so it depend on what kind of unit you deploy and how deep it is.
Anyway, it tooks to long to face a fast attack.
Take a look on different groups sides, where you will see marching romans in videos and get an impression how long these mostly small groups take.
Also a visit in the momentary army show you how long big units need to get the front arund.