rho: command not found

Have You tried accessing the binary with the full path?

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/rho - from package: rho

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