roqet: 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/roqet - from package: rasqal

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

On Debian possible default full paths are:

/usr/bin/roqet - from package: rasqal-utils

You may install the required package with command apt-get install {package}

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