I think ```name = "root_v5.34.14"``` confuses the version parsing logic in nix. Please change it to

```
version = "5.34.14";
name = "root-${version}";
```

So that nix-env sees the package name as "root" and is aware of the version number. (And update the fetchurl.url accordingly, i.e. ```root_v${version}```)