Originally Posted by tfar

Tell the others to have breakfast at their own pace at a place of their choosing in T2. You then make your way over to T2 and meet them at the ticket office for the RER where they will have already bought you a ticket.

There is a shuttle from T1 to T2. I think it takes roughly ten minutes. Others will certainly chime in. The RER stop for T1 is not directly under the airport as it is for T2. So you either need to take a shuttle to the RER stop of T1 or you take the shuttle to T2 and then take the RER from there.

Till