Latest bios beta P2.50 03/11/2018 already has NVMe support.
Donations via PAYPAL / REVOLUT, if u think the guy deserves it, else to the Win-Raid community on the bottom of the page, as it deserves for all the gathered information.
Used to have 3 Asrock Z87 Extreme11/ac and I can confirm that any BIOS version after 2016/6/29 for your motherboard will support NVMe drives. Luckily my motherboard have official BIOS release to support NVMe (require an adapter) - I can run at full speed of my Samsung 960 Evo with Asus Hyper M.2 x4 card.