When did you install the NUC and, when you did, did you install in BIOS mode? In this case, Roon OS updates only to version 1.0 build 259 and doesn’t have Tailscale.
Tailscale on ROCK requires Roon OS 2.1 build 271 or higher, and you get this only if ROCK was installed in UEFI mode.
If you originally installed in BIOS, you need to reinstall.
It might support BIOS installs in the future (see the release notes) but nobody knows when