Is it possible to read the string into an Arduino (Uno)
Yes, it is.
and then remove the ROT line
The ROT portion is not a line, but, you can parse the string (strtok() would be useful), and assemble an array of characters to send.
and send it out again (on a second serial port)
Have you counted serial ports on the Uno? There is one.
You could, however, use NewSoftSerial to create a software serial port, to send data out. Whatever you are sending it to needs to be connected to the appropriate pins (and ground).