/etc/modprobe.d/wifi-roaming.conf # Any name works.

options mac80211 probe_wait_ms=100  # default: 500
options mac80211 max_probe_tries=1  # default: 5
options mac80211 beacon_loss_count=1  # default: 7

Live update (as root):

echo "100" > /sys/module/mac80211/parameters/probe_wait_ms
echo "1" > /sys/module/mac80211/parameters/max_probe_tries
echo "1" > /sys/module/mac80211/parameters/beacon_loss_count