rscreen: 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 Debian possible default full paths are:

/usr/bin/rscreen - from package: autossh

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

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