As it can be expected from Apple, there is no user interface to adjust or change the wifi roaming agressiveness.
This is VERY IMPORTANT if for example you use Macbooks in a very dense wifi environment. If you have a Macbook that’s dropping packets when roaming or having trouble roaming from AP to AP, then open a terminal and run the following.
sudo /System/Library/PrivateFrameworks/Apple80211.framework/Versions/A/Resources/airport prefs joinMode=Strongest
Of the options available, the “strongest” option tells the wifi drivers on the Macbook to connect to the AP with the strongest (and thus hopefully the closest) AP, when multiple APs are available to connect to. Apple has configured the default setting to keep you connected to the same AP as long as possible, even if a better one is available. This is great at home, but not in a corporate environment.
Here are the other options available: