Yes, FT is not necessary for roaming, but it accelerates authentication to the new AP when roaming. This is especially noticable with EAP authentication, because it saves several roundtrips. With PSK, FT will save a few ms, but you will probably not notice any difference.
By the way: I only enable FT (over the air) and keep FT-over-DS disabled everywhere. Depending on the connection quality to the previous AP, FT-over-DS with PSK can be slower than no FT at all!
Edit: YouTube video recommendation: https://www.youtube.com/watch?v=4Ua2lI6HBhE