gnroff: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/gnroff - from package: groff

You may install the required package with command yum install {package}

Error in other languages:
gnroff: bevel nie gevind nie
gnroff: comandă negăsită
gnroff: comando não encontrado
gnroff: commande introuvable
gnroff: command not found
gnroff: käsku ei ole
gnroff: không tìm thấy lệnh
gnroff: komanda nerasta
gnroff: Kommando nicht gefunden.
gnroff: kommandot finns inte
gnroff: komut yok
gnroff: nie znaleziono polecenia
gnroff: níor aimsíodh an t-ordú
gnroff: no se encontró la orden
gnroff: no s'ha trobat l'ordre
gnroff: opdracht niet gevonden
gnroff: parancs nem található
gnroff: perintah tidak ditemukan
gnroff: príkaz nenájdený
gnroff: příkaz nenalezen
gnroff: команда не найдена
gnroff: командата не е открита
gnroff: 命令找不到
gnroff: コマンドが見つかりません