Many thanks for the detailed reply Michael.
When you say "Roaming decisions are made by the client radio driver/supplicant", does this mean - e.g. for laptops - that setting the roaming aggressiveness on the Wireless NIC driver is the only way of controlling roaming?
Otherwise, are the following methods also able to control roaming behaviour to some degree?
1. Smart-Roam functionality - configurable via SSH/CLI - which causes the AP to pretend to go out of range and force roaming (see https://supportqa.ruckuswireless.com/answers/000002277)
2. 802.11r fast transition method and 802.11k ability to send Wi-Fi clients the best potential access points for roaming (as far as I understand, these features can only be enabled by purchasing a controller/Zone Director)
Do you know if the above 2 methods are able to help us improve roaming behaviour?