All of the walkthroughs and videos I've seen of the RER ticket machines show the machine saying that the RER ticket is valid from the station the machine is in. Is it possible to buy RER tickets from a different station? For instance, in my particular case, my hotel is near Crimée, and I need RER tickets from Pont du l'Alma to Versailles (and back) and Gare du Nord to CDG, and I'd rather get those tickets all at once and ahead of time at Crimée. Is there a way to specify a different origin station on those machines?
Yes you can purchase Paris RER train tickets for any trip you want from any RER/Metro or Transilien train ticket office. Use the ticket window and they will customize the ticket for you (if necessary).