yes nixos allows you to roll back even if you nuke the kernel. your entire system is immutable in each state. it's nearly imposible to get your machine into an unrecoverable state.
Discussion
Protonvpn and onlykey apps are both mandatory part of my workflow and both busted in nixos after 3 days of messing around. I've decided give up and do manjaro with BTRFS snapshots instead. Nuke completed, paving now.